In Quantum Information Theory(QIT) the classical measures of information content in probability distributions are replaced by the corresponding resultant entropic descriptors containing the nonclassical terms generate...In Quantum Information Theory(QIT) the classical measures of information content in probability distributions are replaced by the corresponding resultant entropic descriptors containing the nonclassical terms generated by the state phase or its gradient(electronic current). The classical Shannon(S[p]) and Fisher(I[p]) information terms probe the entropic content of incoherent local events of the particle localization, embodied in the probability distribution p, while their nonclassical phase-companions, S[ Φ ] and I[ Φ ], provide relevant coherence information supplements.Thermodynamic-like couplings between the entropic and energetic descriptors of molecular states are shown to be precluded by the principles of quantum mechanics. The maximum of resultant entropy determines the phase-equilibrium state, defined by "thermodynamic" phase related to electronic density,which can be used to describe reactants in hypothetical stages of a bimolecular chemical reaction.Information channels of molecular systems and their entropic bond indices are summarized, the complete-bridge propagations are examined, and sequential cascades involving the complete sets of the atomic-orbital intermediates are interpreted as Markov chains. The QIT description is applied to reactive systems R = A―B, composed of the Acidic(A) and Basic(B) reactants. The electronegativity equalization processes are investigated and implications of the concerted patterns of electronic flows in equilibrium states of the complementarily arranged substrates are investigated. Quantum communications between reactants are explored and the QIT descriptors of the A―B bond multiplicity/composition are extracted.展开更多
The electronic structures,optical dielectric functions,elastic properties,and lattice dynamics of Ba2ZnWO6 have been investigated by using the generalized gradient approximation.The density of states and distributions...The electronic structures,optical dielectric functions,elastic properties,and lattice dynamics of Ba2ZnWO6 have been investigated by using the generalized gradient approximation.The density of states and distributions of charge density show that O and Ba tend toward ionic bond,but O and W or Zn display the covalent bond character.The calculated energy band structure shows that Ba2ZnWO6 is a wide indirect band gap semiconductor.The static value 2.28 of the refractive index is attained.The analysis of the elastic properties of Ba2ZnWO6 indicates a rather weak elastic anisotropy.The phonon dispersion is calculated,suggesting no structural instability,which is agreement with the recent low temperature neutron diffraction experiments.The mensurability C v(phonon heat capacity) as the function of the temperature is also calculated to judge our results for future experiment.展开更多
The structural, electronic and optical properties of rocksalt CdO have been studied using the plane-wave-based pseudo-potential density functional theory within generalized gradient approximation. The calculated latti...The structural, electronic and optical properties of rocksalt CdO have been studied using the plane-wave-based pseudo-potential density functional theory within generalized gradient approximation. The calculated lattice parameters are in agreement with previous experimental work. The band structure, density of states, and Mulliken charge population are obtained, which indicates that rocksalt CdO having the properties of a halfmetal due to an indirect band gap of -0.51eV. The mechanical properties show that rocksalt CdO is mechanically stable, isotropic and malleable. Significantly, we propose a correct value for ε1(0) of about 4.75, which offers theoretical data for the design and application for rocksalt CdO in optoelectronic materials.展开更多
Quantum chemistry density-functional theory (DFT)B3LYP method with 6-31G+* basis set has been empolyed to study the electronic structure and IR spectrum of Huperzine A. The calculation result showed that the character...Quantum chemistry density-functional theory (DFT)B3LYP method with 6-31G+* basis set has been empolyed to study the electronic structure and IR spectrum of Huperzine A. The calculation result showed that the characteristic of the predicted IR bands was in general consistent with the experimental spectrum. 45 vibration modes were assigned clearly from the total of 102 vibration bands. The strongest IR-intensive band corresponds to the stretching vibration of the C O bond of the pyridone ring, and the highest frequency band belongs to the pyridone N H stretch. The investigation showed that the obvious differences between the calculated bands and the experimental spectrum existed at the bands involving the hydrogen atoms of amino and pyridone amide groups, which could form intermolecular hydrogen bond with other Huperzine A in the crystal structure. The hydrogen bonds can not only affect the orientation of these hydrogen atoms, but also can affect the force property of the chemical bond, which can change the vibrational frequencies.展开更多
We investigate the electronic structure ofβ-uranium,which has five nonequivalent atomic sites in its unit cell,by means of the density functional theory plus Hubbard-U correction with U from linear response calculati...We investigate the electronic structure ofβ-uranium,which has five nonequivalent atomic sites in its unit cell,by means of the density functional theory plus Hubbard-U correction with U from linear response calculation.It is found that the 5f electronic correlations inβ-uranium are moderate.More interestingly,their strengths are site selective,depending on the local atomic environment of the present uranium atom.As a consequence,the occupation matrices and partial 5f density of states ofβ-uranium manifest site dependence.In addition,the complicate experimental structure ofβ-uranium could be well reproduced within this theoretical framework.展开更多
First-principles calculation of muons in ionic fluorides has been proposed recently.However,there is a considerable difference between the obtained F-μbond length and the experimental data obtained by muon spin relax...First-principles calculation of muons in ionic fluorides has been proposed recently.However,there is a considerable difference between the obtained F-μbond length and the experimental data obtained by muon spin relaxation(μSR).Considering that the difference may be caused by ignoring the quantum effect of muons,we use two-component density functional theory(TCDFT)to consider the quantized muon and recalculate the bond length and theμSR depolarization spectrum.After testing several muon-electron correlation,we show that TCDFT can give better results than the commonly used“DFT+μ”.展开更多
Separation of ethane from ethylene is a very important but challenging process in the petrochemical industry.Finding an alternative method would reduce the energy needed to make 170 million tons of ethylene manufactur...Separation of ethane from ethylene is a very important but challenging process in the petrochemical industry.Finding an alternative method would reduce the energy needed to make 170 million tons of ethylene manufactured worldwide each year.Adsorptive separation using C2H6-selective porous materials to directly produce high-purity C2H4 is more energy-efficient.We herein report the"reversed C2H6/C2H4 adsorption"in a metal–organic framework Cr-BTC via the introduction of oxygen on its open metal sites.The oxidized Cr-BTC(O2)can bind C2H6 over C2H4 through the active Cr-superoxo sites,which was elucidated by the gas sorption isotherms and density functional theory calculations.This material thus exhibits a good performance for the separation of 50/50 C2H6/C2H4 mixtures to produce 99.99%pure C2H4 in a single separation operation.展开更多
The combination of 5,5'-bistetrazole-1,1'-diolate(TKX-50) and ammonium perchlorate(AP) can make greater use of the chemical energy of TKX-50 based energetic materials.The research on the interaction mechanism ...The combination of 5,5'-bistetrazole-1,1'-diolate(TKX-50) and ammonium perchlorate(AP) can make greater use of the chemical energy of TKX-50 based energetic materials.The research on the interaction mechanism between TKX-50 and AP is very important for designing TKX-50-AP compounds and judging the formation feasibility of composite particles,which can lay a theoretical foundation for the preparation of TKX-50-AP mixed crystals and the application of TKX-50 in propellant,propellant and explosive.Herein,in order to research the interaction mechanism between TKX-50 and AP,density-functional theory calculation was applied to optimize three configurations of TKX-50-AP compounds.The geometry structure,electrostatic potential and binding energy of the compounds were predicted,and the electronic density topological analysis was also carried out.Then TKX-50-AP mixed crystals structures were constructed,and the radial distribution function of H-O and H-N in mixed crystals was calculated.Finally,solvent/non-solvent method was applied to prepare TKX-50-AP composites,and the infrared spectro scopy and the non-isothermal decomposition perfo rmance of the composites were characterized.Results show that the superposition of positive charges in TKX-50 molecule and negative charges in AP makes the electrostatic potential distributions of TKX-50-AP compounds different from that of TKX-50 and AP.The interaction energies of TKX-50-AP 1,TKX-50-AP 2 and TKX-50-AP 3 are 39.743 kJ/mol,61.206 kJ/mol and 27.702 kJ/mol,respectively.The interaction between TKX-50 molecules and AP molecules in TKX-50-AP mixed crystals both depends on hydrogen bonds and van der Waals force,and the number and strength of hydrogen bonds are significantly greater than that of van der Waals force.The composition of AP and TKX-50 makes the absorption peak of the five-membered rings and NH_3 OH^+ of TKX-50 shift to low wavenumber in the infrared spectroscopy.In general,TKX-50 interacts with AP via hydrogen bonds and van der Waals force,and the calculated results are in good agreement with the experimental results.The composition of TKX-50 and AP can also prolong the decomposition process.展开更多
The electronic structure and magnetic properties of the transition-metal(TM) atoms(Sc–Zn, Pt and Au) doped zigzag GaN single-walled nanotubes(NTs) are investigated using first-principles spin-polarized density functi...The electronic structure and magnetic properties of the transition-metal(TM) atoms(Sc–Zn, Pt and Au) doped zigzag GaN single-walled nanotubes(NTs) are investigated using first-principles spin-polarized density functional calculations. Our results show that the bindings of all TM atoms are stable with the binding energy in the range of 6–16 eV. The Sc- and V-doped GaN NTs exhibit a nonmagnetic behavior. The GaN NTs doped with Ti, Mn, Ni, Cu and Pt are antiferromagnetic. On the contrary, the Cr-, Fe-, Co-, Zn- and Au-doped GaN NTs show the ferromagnetic characteristics. The Mn- and Codoped GaN NTs induce the largest local moment of 4μB among these TM atoms. The local magnetic moment is dominated by the contribution from the substitutional TM atom and the N atoms bonded with it.展开更多
Ammonia has been recognized as the future renewable energy fuel because of its wide-ranging applications in H_(2) storage and transportation sector.In order to avoid the environmentally hazardous Haber-Bosch process,r...Ammonia has been recognized as the future renewable energy fuel because of its wide-ranging applications in H_(2) storage and transportation sector.In order to avoid the environmentally hazardous Haber-Bosch process,recently,the third-generation ambient ammonia synthesis has drawn phenom-enal attention and thus tremendous efforts are devoted to developing efficient electrocatalysts that would circumvent the bottlenecks of the electrochemical nitrogen reduction reaction(NRR)like competitive hydrogen evolution reac-tion,poor selectivity of N_(2) on catalyst surface.Herein,we report the synthesis of an oxygen-functionalized boron carbonitride matrix via a two-step pyrolysis technique.The conductive BNCO(1000)architecture,the compatibility of B-2p_(z) orbital with the N-2p_(z) orbital and the charging effect over B due to the C and O edge-atoms in a pentagon altogether facilitate N_(2) adsorption on the B edge-active sites.The optimum electrolyte acidity with 0.1 M HCl and the lowered anion crowding effect aid the protonation steps of NRR via an associative alternating pathway,which gives a sufficiently high yield of ammonia(211.5μg h^(−1) mg_(cat)^(−1))on the optimized BNCO(1000)catalyst with a Faradaic efficiency of 34.7%at−0.1 V vs RHE.This work thus offers a cost-effective electrode material and provides a contemporary idea about reinforcing the charging effect over the secured active sites for NRR by selectively choosing the electrolyte anions and functionalizing the active edges of the BNCO(1000)catalyst.展开更多
The addition of electrons to form gas-phase multiply charged anions(MCAs)normally requires sophisticated experiments or calculations.In this work,the factors stabilizing the MCAs,the maximum electron uptake of gas-pha...The addition of electrons to form gas-phase multiply charged anions(MCAs)normally requires sophisticated experiments or calculations.In this work,the factors stabilizing the MCAs,the maximum electron uptake of gas-phase molecules,X,and the electronic stability of MCAs X^(Q-),are discussed.The drawbacks encountered when applying computational and/or conceptual density functional theory(DFT)to MCAs are highlighted.We develop and test a different model based on the valence-state concept.As in DFT,the electronic energy,E(N,v_(ex)),is a continuous function of the average electron number,N,and the external potential,v_(ex),of the nuclei.The valence-state-parabola is a second-order polynomial that allows extending E(N,v_(ex))to dianions and higher MCAs.The model expresses the maximum electron acceptance,Q_(max),and the higher electron affinities,A_Q,as simple functions of the firstelectron affinity,A_1,and the ionization energy,I,of the"ancestor"system.Thus,the maximum electron acceptance is Q_(max,calc)=1+12A_1/7(I-A_1).The ground-state parabola model of the conceptual DFT yields approximately half of this value,and it is termed Q_(max,GS)=?+A_1/(I-A_1).A large variety of molecules are evaluated including fullerenes,metal clusters,super-pnictogens,super-halogens(OF_3),super-alkali species(OLi_3),and neutral or charged transition-metal complexes,AB_(m )L_n^(0/+/-).The calculated second electron affinity A_(2,calc)=A_1-(7/12)(I-A_1)is linearly correlated to the literature references A_(2,lit) with a correlation coefficient R=0.998.A_2 or A_3 values are predicted for further 24 species.The appearance sizes,n_(ap)^(3-),of triply charged anionic clusters and fullerenes are calculated in agreement with the literature.展开更多
In the present paper we give a detailed report on the results of our first-principles investigations of Ar adsorptions at the four high symmetry sites on M(111)(M = Pd,Pt,Cu,and Rh) surfaces.Our studies indicate that ...In the present paper we give a detailed report on the results of our first-principles investigations of Ar adsorptions at the four high symmetry sites on M(111)(M = Pd,Pt,Cu,and Rh) surfaces.Our studies indicate that the most stable adsorption sites of Ar on Pd(111) and Pt(111) surfaces are found to be the fcc-hollow sites.However,for Ar adsorptions on Cu(111) and Rh(111) surfaces,the most favorable site is the on-top site.The density of states(DOS) is analyzed for Ar adsorption on M(111) surfaces,and it is concluded that the adsorption behavior is dominated by the interaction between 3s,3p orbits of Ar atoms and the d orbit of the base metal atoms.展开更多
We investigate the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons(APNRs) containing atomic vacancies with different distributions and concentrations using ab initio density fun...We investigate the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons(APNRs) containing atomic vacancies with different distributions and concentrations using ab initio density functional calculations. It is found that the atomic vacancies are easier to form and detain at the edge region rather than a random distribution through analyzing formation energy and diffusion barrier. The highly local defect states are generated at the vicinity of the Fermi level, and emerge a deep-to-shallow transformation as the width increases after introducing vacancies in APNRs.Moreover, the electrical transport of APNRs with vacancies is enhanced compared to that of the perfect counterparts. Our results provide a theoretical guidance for the further research and applications of PNRs through defect engineering.展开更多
A brief history of the impurity theories in semiconductors is provided. A bound exciton model is proposed for both donor-and acceptor-like impurities and point defects, which offers a unified understanding for "s...A brief history of the impurity theories in semiconductors is provided. A bound exciton model is proposed for both donor-and acceptor-like impurities and point defects, which offers a unified understanding for "shallow" and "deep"impurities and point defects. The underlying physics of computational results using different density-functional theorybased approaches are discussed and interpreted in the framework of the bound exciton model.展开更多
Very recently,experimental evidence showed that the hydrogen is retained in dithiol-terminated single-molecule junction under the widely adopted preparation conditions,which is in contrast to the accepted view[Nat.Che...Very recently,experimental evidence showed that the hydrogen is retained in dithiol-terminated single-molecule junction under the widely adopted preparation conditions,which is in contrast to the accepted view[Nat.Chem.11351(2019)].However,the hydrogen is generally assumed to be lost in the previous physical models of single-molecule junctions.Whether the retention of the hydrogen at the gold-sulfur interface exerts a significant effect on the theoretical prediction of spin transport properties is an open question.Therefore,here in this paper we carry out a comparative study of spin transport in M-tetraphenylporphyrin-based(M=V,Cr,Mn,Fe,and Co;M-TPP)single-molecule junction through Au-SR and Au-S(H)R bondings.The results show that the hydrogen at the gold-sulfur interface may dramatically affect the spin-filtering efficiency of M-TPP-based single-molecule junction,depending on the type of transition metal ions embedded into porphyrin ring.Moreover,we find that for the Co-TPP-based molecular junction,the hydrogen at the gold-sulfur interface has no obvious effect on transmission at the Fermi level,but it has a significant effect on the spin-dependent transmission dip induced by the quantum interference on the occupied side.Thus the fate of hydrogen should be concerned in the physical model according to the actual preparation condition,which is important for our fundamental understanding of spin transport in the single-molecule junctions.Our work also provides guidance in how to experimentally identify the nature of gold-sulfur interface in the single-molecule junction with spin-polarized transport.展开更多
Controlling the spin transport at the single-molecule level,especially without the use of ferromagnetic contacts,becomes a focus of research in spintronics.Inspired by the progress on atomic-level molecular synthesis,...Controlling the spin transport at the single-molecule level,especially without the use of ferromagnetic contacts,becomes a focus of research in spintronics.Inspired by the progress on atomic-level molecular synthesis,through firstprinciples calculations,we investigate the spin-dependent electronic transport of graphene nanoflakes with side-bonded functional groups,contacted by atomic carbon chain electrodes.It is found that,by rotating the functional group,the spin polarization of the transmission at the Fermi level could be switched between completely polarized and unpolarized states.Moreover,the transition between spin-up and spin-down polarized states can also be achieved,operating as a dual-spin filter.Further analysis shows that,it is the spin-dependent shift of density of states,caused by the rotation,that triggers the shift of transmission peaks,and then results in the variation of spin polarization.Such a feature is found to be robust to the length of the nanoflake and the electrode material,showing great application potential.Those findings may throw light on the development of spintronic devices.展开更多
Interfacial charge recombination is a main issue causing the efficiency loss of the perovskite solar cells(PSCs).Here,ferroelectric Ba_(0.75)Sr_(0.25)TiO_(3)(BST)is introduced as a polarization tunable layer to promot...Interfacial charge recombination is a main issue causing the efficiency loss of the perovskite solar cells(PSCs).Here,ferroelectric Ba_(0.75)Sr_(0.25)TiO_(3)(BST)is introduced as a polarization tunable layer to promote the interfacial charge transfer of the PSCs.The coexistence of ferroelectric polarization and charge carriers in BST is confirmed by density functional theory(DFT)calculations.Experimental characterization demonstrates the polarization reversal and the existence of domain in BST film.The BST film conductivity is tested as 2.98×10^(-4)S/cm,which is comparable to the TiO;being used as the electron transporting layer(ETL)in PSCs.The calculations results prove that BST can be introduced into the PSCs and the interfacial charge transfer can be tuned by ferroelectric polarization.Thus,we fabricated the BST-based PSCs with a champion power conversion efficiency(PCE)of 19.05%after poling.展开更多
We have investigated the electronic states of clean Fe(001) and oxygen adsorbed Fe(001)–p(1 × 1)-O films epitaxially grown on MgO(001) substrates by means of polarization-dependent angle-resolved photoemission s...We have investigated the electronic states of clean Fe(001) and oxygen adsorbed Fe(001)–p(1 × 1)-O films epitaxially grown on MgO(001) substrates by means of polarization-dependent angle-resolved photoemission spectroscopy(ARPES)and extensive density-functional theory(DFT) calculations. The observed Fermi surfaces and band dispersions of pure Fe near the Fermi level were modified upon oxygen adsorption. By the detailed comparison of ARPES and DFT results of the oxygen adsorbed Fe surface, we have clarified the orbital-dependent p–d hybridization in the topmost and second Fe layers.Furthermore, the observed energy levels and Fermi wave numbers for the oxygen adsorbed Fe surface were deviated from the DFT calculations depending on the orbital characters and momentum directions, indicating an anisotropic interplay of the electron correlation and p–d hybridization effects in the surface region.展开更多
The effect of strain on charge density wave(CDW)order inα-U is investigated within the framework of relativistic density-functional theory.The energetical stability ofα-U with CDW distortion is enhanced by the tensi...The effect of strain on charge density wave(CDW)order inα-U is investigated within the framework of relativistic density-functional theory.The energetical stability ofα-U with CDW distortion is enhanced by the tensile strain along a and b axes,which is similar to the case of negative pressure and normal.However,the tensile strain along c axis suppresses the energetical stability of CDW phase.This abnormal effect could be understood from the emergence of a new onedimensional atomic chain along c axis inα-U.Furthermore,this effect is supported by the calculations of Fermi surface and phonon mode,in which the topological objects and the dynamical instability show opposite behaviors between strains along a/b and c axes.展开更多
Phosgene is highly toxic, and it plays a role in the depletion of the ozone layer. The ground state geometric structure and spectral characteristic of phosgene in various external electric fields were calculated via t...Phosgene is highly toxic, and it plays a role in the depletion of the ozone layer. The ground state geometric structure and spectral characteristic of phosgene in various external electric fields were calculated via the density-functional theory (DFT) and time-dependent density-functional theory (TDDFT) with the B3LYP/6-31+G(d) basis set. With external electric field, the structure of phosgene changed significantly. With increasing electric field, the bond lengths of 1C-3Cl and 1C-4Cl increased;the total energy and energy gap initially increased and then decreased, whereas the dipole moment initially decreased and then increased. Most of the IR vibrational frequencies were redshifted. The wavelength of the singlet excited state increased, reflecting a red shift, and the oscillator strengths of most transitions belonged to forbidden transitions. These results are of great significance for studying the dissociation of phosgene in external electric field.展开更多
文摘In Quantum Information Theory(QIT) the classical measures of information content in probability distributions are replaced by the corresponding resultant entropic descriptors containing the nonclassical terms generated by the state phase or its gradient(electronic current). The classical Shannon(S[p]) and Fisher(I[p]) information terms probe the entropic content of incoherent local events of the particle localization, embodied in the probability distribution p, while their nonclassical phase-companions, S[ Φ ] and I[ Φ ], provide relevant coherence information supplements.Thermodynamic-like couplings between the entropic and energetic descriptors of molecular states are shown to be precluded by the principles of quantum mechanics. The maximum of resultant entropy determines the phase-equilibrium state, defined by "thermodynamic" phase related to electronic density,which can be used to describe reactants in hypothetical stages of a bimolecular chemical reaction.Information channels of molecular systems and their entropic bond indices are summarized, the complete-bridge propagations are examined, and sequential cascades involving the complete sets of the atomic-orbital intermediates are interpreted as Markov chains. The QIT description is applied to reactive systems R = A―B, composed of the Acidic(A) and Basic(B) reactants. The electronegativity equalization processes are investigated and implications of the concerted patterns of electronic flows in equilibrium states of the complementarily arranged substrates are investigated. Quantum communications between reactants are explored and the QIT descriptors of the A―B bond multiplicity/composition are extracted.
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. 2013QNA32)
文摘The electronic structures,optical dielectric functions,elastic properties,and lattice dynamics of Ba2ZnWO6 have been investigated by using the generalized gradient approximation.The density of states and distributions of charge density show that O and Ba tend toward ionic bond,but O and W or Zn display the covalent bond character.The calculated energy band structure shows that Ba2ZnWO6 is a wide indirect band gap semiconductor.The static value 2.28 of the refractive index is attained.The analysis of the elastic properties of Ba2ZnWO6 indicates a rather weak elastic anisotropy.The phonon dispersion is calculated,suggesting no structural instability,which is agreement with the recent low temperature neutron diffraction experiments.The mensurability C v(phonon heat capacity) as the function of the temperature is also calculated to judge our results for future experiment.
文摘The structural, electronic and optical properties of rocksalt CdO have been studied using the plane-wave-based pseudo-potential density functional theory within generalized gradient approximation. The calculated lattice parameters are in agreement with previous experimental work. The band structure, density of states, and Mulliken charge population are obtained, which indicates that rocksalt CdO having the properties of a halfmetal due to an indirect band gap of -0.51eV. The mechanical properties show that rocksalt CdO is mechanically stable, isotropic and malleable. Significantly, we propose a correct value for ε1(0) of about 4.75, which offers theoretical data for the design and application for rocksalt CdO in optoelectronic materials.
文摘Quantum chemistry density-functional theory (DFT)B3LYP method with 6-31G+* basis set has been empolyed to study the electronic structure and IR spectrum of Huperzine A. The calculation result showed that the characteristic of the predicted IR bands was in general consistent with the experimental spectrum. 45 vibration modes were assigned clearly from the total of 102 vibration bands. The strongest IR-intensive band corresponds to the stretching vibration of the C O bond of the pyridone ring, and the highest frequency band belongs to the pyridone N H stretch. The investigation showed that the obvious differences between the calculated bands and the experimental spectrum existed at the bands involving the hydrogen atoms of amino and pyridone amide groups, which could form intermolecular hydrogen bond with other Huperzine A in the crystal structure. The hydrogen bonds can not only affect the orientation of these hydrogen atoms, but also can affect the force property of the chemical bond, which can change the vibrational frequencies.
基金supported by the National Natural Science Foundation of China (Grant Nos.22176181,11874329,11934020,and U1930121)the Foundation of the President of China Academy of Engineering Physics (Grant No.YZJJZQ2022011)the Foundation of Science and Technology on Surface Physics and Chemistry Laboratory (Grant No.WDZC202101)。
文摘We investigate the electronic structure ofβ-uranium,which has five nonequivalent atomic sites in its unit cell,by means of the density functional theory plus Hubbard-U correction with U from linear response calculation.It is found that the 5f electronic correlations inβ-uranium are moderate.More interestingly,their strengths are site selective,depending on the local atomic environment of the present uranium atom.As a consequence,the occupation matrices and partial 5f density of states ofβ-uranium manifest site dependence.In addition,the complicate experimental structure ofβ-uranium could be well reproduced within this theoretical framework.
基金financially supported by the National Natural Science Foundation of China(Grant No.12005221)。
文摘First-principles calculation of muons in ionic fluorides has been proposed recently.However,there is a considerable difference between the obtained F-μbond length and the experimental data obtained by muon spin relaxation(μSR).Considering that the difference may be caused by ignoring the quantum effect of muons,we use two-component density functional theory(TCDFT)to consider the quantized muon and recalculate the bond length and theμSR depolarization spectrum.After testing several muon-electron correlation,we show that TCDFT can give better results than the commonly used“DFT+μ”.
基金the financial support from the National Natural Science Foundation of China(Nos.21606163 and 21878205)Coal Bed Methane Joint Foundation of Shanxi(2016012006)+2 种基金Foundation of State Key Laboratory of Coal Conversion(J18-19-610)Welch Foundation(grant AX-1730)the Distinguished Scientist Fellowship Program(DSFP)at KSU.
文摘Separation of ethane from ethylene is a very important but challenging process in the petrochemical industry.Finding an alternative method would reduce the energy needed to make 170 million tons of ethylene manufactured worldwide each year.Adsorptive separation using C2H6-selective porous materials to directly produce high-purity C2H4 is more energy-efficient.We herein report the"reversed C2H6/C2H4 adsorption"in a metal–organic framework Cr-BTC via the introduction of oxygen on its open metal sites.The oxidized Cr-BTC(O2)can bind C2H6 over C2H4 through the active Cr-superoxo sites,which was elucidated by the gas sorption isotherms and density functional theory calculations.This material thus exhibits a good performance for the separation of 50/50 C2H6/C2H4 mixtures to produce 99.99%pure C2H4 in a single separation operation.
文摘The combination of 5,5'-bistetrazole-1,1'-diolate(TKX-50) and ammonium perchlorate(AP) can make greater use of the chemical energy of TKX-50 based energetic materials.The research on the interaction mechanism between TKX-50 and AP is very important for designing TKX-50-AP compounds and judging the formation feasibility of composite particles,which can lay a theoretical foundation for the preparation of TKX-50-AP mixed crystals and the application of TKX-50 in propellant,propellant and explosive.Herein,in order to research the interaction mechanism between TKX-50 and AP,density-functional theory calculation was applied to optimize three configurations of TKX-50-AP compounds.The geometry structure,electrostatic potential and binding energy of the compounds were predicted,and the electronic density topological analysis was also carried out.Then TKX-50-AP mixed crystals structures were constructed,and the radial distribution function of H-O and H-N in mixed crystals was calculated.Finally,solvent/non-solvent method was applied to prepare TKX-50-AP composites,and the infrared spectro scopy and the non-isothermal decomposition perfo rmance of the composites were characterized.Results show that the superposition of positive charges in TKX-50 molecule and negative charges in AP makes the electrostatic potential distributions of TKX-50-AP compounds different from that of TKX-50 and AP.The interaction energies of TKX-50-AP 1,TKX-50-AP 2 and TKX-50-AP 3 are 39.743 kJ/mol,61.206 kJ/mol and 27.702 kJ/mol,respectively.The interaction between TKX-50 molecules and AP molecules in TKX-50-AP mixed crystals both depends on hydrogen bonds and van der Waals force,and the number and strength of hydrogen bonds are significantly greater than that of van der Waals force.The composition of AP and TKX-50 makes the absorption peak of the five-membered rings and NH_3 OH^+ of TKX-50 shift to low wavenumber in the infrared spectroscopy.In general,TKX-50 interacts with AP via hydrogen bonds and van der Waals force,and the calculated results are in good agreement with the experimental results.The composition of TKX-50 and AP can also prolong the decomposition process.
基金Project supported by the National Basic Research Program of China(Grant No.2012CB619304)the National Natural Science Foundation of China(Grant Nos.51072007,91021017,11364030,and 11047018)the Beijing Natural Science Foundation,China(Grant No.1112007)
文摘The electronic structure and magnetic properties of the transition-metal(TM) atoms(Sc–Zn, Pt and Au) doped zigzag GaN single-walled nanotubes(NTs) are investigated using first-principles spin-polarized density functional calculations. Our results show that the bindings of all TM atoms are stable with the binding energy in the range of 6–16 eV. The Sc- and V-doped GaN NTs exhibit a nonmagnetic behavior. The GaN NTs doped with Ti, Mn, Ni, Cu and Pt are antiferromagnetic. On the contrary, the Cr-, Fe-, Co-, Zn- and Au-doped GaN NTs show the ferromagnetic characteristics. The Mn- and Codoped GaN NTs induce the largest local moment of 4μB among these TM atoms. The local magnetic moment is dominated by the contribution from the substitutional TM atom and the N atoms bonded with it.
基金A.B.acknowledges INST Mohali for providing instrumental support and fellowship.R.S.D.acknowledges Department of Science and Technology,Science and Engineering Research Board(DST SERB)(CRG/2020/005683)funding agency for financial supportRT thanks Board of Research in Nuclear Sciences(BRNS),India,for financial support(Grant No.37(2)/20/14/2018-BRNS/37144)National Supercomputer Mission(NSM),India,for financial support(Ref No:DST/NSM/R&D_HPC_Applications/2021/19).
文摘Ammonia has been recognized as the future renewable energy fuel because of its wide-ranging applications in H_(2) storage and transportation sector.In order to avoid the environmentally hazardous Haber-Bosch process,recently,the third-generation ambient ammonia synthesis has drawn phenom-enal attention and thus tremendous efforts are devoted to developing efficient electrocatalysts that would circumvent the bottlenecks of the electrochemical nitrogen reduction reaction(NRR)like competitive hydrogen evolution reac-tion,poor selectivity of N_(2) on catalyst surface.Herein,we report the synthesis of an oxygen-functionalized boron carbonitride matrix via a two-step pyrolysis technique.The conductive BNCO(1000)architecture,the compatibility of B-2p_(z) orbital with the N-2p_(z) orbital and the charging effect over B due to the C and O edge-atoms in a pentagon altogether facilitate N_(2) adsorption on the B edge-active sites.The optimum electrolyte acidity with 0.1 M HCl and the lowered anion crowding effect aid the protonation steps of NRR via an associative alternating pathway,which gives a sufficiently high yield of ammonia(211.5μg h^(−1) mg_(cat)^(−1))on the optimized BNCO(1000)catalyst with a Faradaic efficiency of 34.7%at−0.1 V vs RHE.This work thus offers a cost-effective electrode material and provides a contemporary idea about reinforcing the charging effect over the secured active sites for NRR by selectively choosing the electrolyte anions and functionalizing the active edges of the BNCO(1000)catalyst.
文摘The addition of electrons to form gas-phase multiply charged anions(MCAs)normally requires sophisticated experiments or calculations.In this work,the factors stabilizing the MCAs,the maximum electron uptake of gas-phase molecules,X,and the electronic stability of MCAs X^(Q-),are discussed.The drawbacks encountered when applying computational and/or conceptual density functional theory(DFT)to MCAs are highlighted.We develop and test a different model based on the valence-state concept.As in DFT,the electronic energy,E(N,v_(ex)),is a continuous function of the average electron number,N,and the external potential,v_(ex),of the nuclei.The valence-state-parabola is a second-order polynomial that allows extending E(N,v_(ex))to dianions and higher MCAs.The model expresses the maximum electron acceptance,Q_(max),and the higher electron affinities,A_Q,as simple functions of the firstelectron affinity,A_1,and the ionization energy,I,of the"ancestor"system.Thus,the maximum electron acceptance is Q_(max,calc)=1+12A_1/7(I-A_1).The ground-state parabola model of the conceptual DFT yields approximately half of this value,and it is termed Q_(max,GS)=?+A_1/(I-A_1).A large variety of molecules are evaluated including fullerenes,metal clusters,super-pnictogens,super-halogens(OF_3),super-alkali species(OLi_3),and neutral or charged transition-metal complexes,AB_(m )L_n^(0/+/-).The calculated second electron affinity A_(2,calc)=A_1-(7/12)(I-A_1)is linearly correlated to the literature references A_(2,lit) with a correlation coefficient R=0.998.A_2 or A_3 values are predicted for further 24 species.The appearance sizes,n_(ap)^(3-),of triply charged anionic clusters and fullerenes are calculated in agreement with the literature.
基金supported by the National Natural Science Foundation of China (Grant No. 11074176)the National Natural Science Foundation of China (Grant No. 10976019)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20100181110080)
文摘In the present paper we give a detailed report on the results of our first-principles investigations of Ar adsorptions at the four high symmetry sites on M(111)(M = Pd,Pt,Cu,and Rh) surfaces.Our studies indicate that the most stable adsorption sites of Ar on Pd(111) and Pt(111) surfaces are found to be the fcc-hollow sites.However,for Ar adsorptions on Cu(111) and Rh(111) surfaces,the most favorable site is the on-top site.The density of states(DOS) is analyzed for Ar adsorption on M(111) surfaces,and it is concluded that the adsorption behavior is dominated by the interaction between 3s,3p orbits of Ar atoms and the d orbit of the base metal atoms.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574080 and 91833302)。
文摘We investigate the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons(APNRs) containing atomic vacancies with different distributions and concentrations using ab initio density functional calculations. It is found that the atomic vacancies are easier to form and detain at the edge region rather than a random distribution through analyzing formation energy and diffusion barrier. The highly local defect states are generated at the vicinity of the Fermi level, and emerge a deep-to-shallow transformation as the width increases after introducing vacancies in APNRs.Moreover, the electrical transport of APNRs with vacancies is enhanced compared to that of the perfect counterparts. Our results provide a theoretical guidance for the further research and applications of PNRs through defect engineering.
基金supported by ARO/MURI (W911NF-101-0524 monitored by Dr. William Clark)ARO/Electronics (W911NF1610263 monitored by Dr. William Clark and Dr. Michele Gerhold)Bissell Distinguished Professorship at UNCC
文摘A brief history of the impurity theories in semiconductors is provided. A bound exciton model is proposed for both donor-and acceptor-like impurities and point defects, which offers a unified understanding for "shallow" and "deep"impurities and point defects. The underlying physics of computational results using different density-functional theorybased approaches are discussed and interpreted in the framework of the bound exciton model.
基金the National Natural Science Foundation of China(Grant Nos.11674092,11804093,and 61764005)the Natural Science Foundation of Hunan Province,China(Grant No.2019JJ40006)+2 种基金the Scientific Research Fund of the Education Department of Hunan Province,China(Grant No.18B368)the Science and Technology Development Plan Project of Hengyang City,China(Grant No.2018KJ121)the Science and Technology Plan Project of Hunan Province,China(Grant No.2016TP1020).
文摘Very recently,experimental evidence showed that the hydrogen is retained in dithiol-terminated single-molecule junction under the widely adopted preparation conditions,which is in contrast to the accepted view[Nat.Chem.11351(2019)].However,the hydrogen is generally assumed to be lost in the previous physical models of single-molecule junctions.Whether the retention of the hydrogen at the gold-sulfur interface exerts a significant effect on the theoretical prediction of spin transport properties is an open question.Therefore,here in this paper we carry out a comparative study of spin transport in M-tetraphenylporphyrin-based(M=V,Cr,Mn,Fe,and Co;M-TPP)single-molecule junction through Au-SR and Au-S(H)R bondings.The results show that the hydrogen at the gold-sulfur interface may dramatically affect the spin-filtering efficiency of M-TPP-based single-molecule junction,depending on the type of transition metal ions embedded into porphyrin ring.Moreover,we find that for the Co-TPP-based molecular junction,the hydrogen at the gold-sulfur interface has no obvious effect on transmission at the Fermi level,but it has a significant effect on the spin-dependent transmission dip induced by the quantum interference on the occupied side.Thus the fate of hydrogen should be concerned in the physical model according to the actual preparation condition,which is important for our fundamental understanding of spin transport in the single-molecule junctions.Our work also provides guidance in how to experimentally identify the nature of gold-sulfur interface in the single-molecule junction with spin-polarized transport.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11705097,11504178,and 11804158)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20170895)the Funding of Jiangsu Innovation Program for Graduate Education(Grant No.KYCX21_0709)
文摘Controlling the spin transport at the single-molecule level,especially without the use of ferromagnetic contacts,becomes a focus of research in spintronics.Inspired by the progress on atomic-level molecular synthesis,through firstprinciples calculations,we investigate the spin-dependent electronic transport of graphene nanoflakes with side-bonded functional groups,contacted by atomic carbon chain electrodes.It is found that,by rotating the functional group,the spin polarization of the transmission at the Fermi level could be switched between completely polarized and unpolarized states.Moreover,the transition between spin-up and spin-down polarized states can also be achieved,operating as a dual-spin filter.Further analysis shows that,it is the spin-dependent shift of density of states,caused by the rotation,that triggers the shift of transmission peaks,and then results in the variation of spin polarization.Such a feature is found to be robust to the length of the nanoflake and the electrode material,showing great application potential.Those findings may throw light on the development of spintronic devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51972266,51672214,and 11904286)the Natural Science Basic Research Program of Shaanxi Province,China(Grant No.2022JZ-01)。
文摘Interfacial charge recombination is a main issue causing the efficiency loss of the perovskite solar cells(PSCs).Here,ferroelectric Ba_(0.75)Sr_(0.25)TiO_(3)(BST)is introduced as a polarization tunable layer to promote the interfacial charge transfer of the PSCs.The coexistence of ferroelectric polarization and charge carriers in BST is confirmed by density functional theory(DFT)calculations.Experimental characterization demonstrates the polarization reversal and the existence of domain in BST film.The BST film conductivity is tested as 2.98×10^(-4)S/cm,which is comparable to the TiO;being used as the electron transporting layer(ETL)in PSCs.The calculations results prove that BST can be introduced into the PSCs and the interfacial charge transfer can be tuned by ferroelectric polarization.Thus,we fabricated the BST-based PSCs with a champion power conversion efficiency(PCE)of 19.05%after poling.
基金Present address Synchrotron Radiation Research Center,National Institutes for Quantum and Radiological Science and Technology,1-1-1 Kouto,Sayo,Hyogo679-5148,Japan
文摘We have investigated the electronic states of clean Fe(001) and oxygen adsorbed Fe(001)–p(1 × 1)-O films epitaxially grown on MgO(001) substrates by means of polarization-dependent angle-resolved photoemission spectroscopy(ARPES)and extensive density-functional theory(DFT) calculations. The observed Fermi surfaces and band dispersions of pure Fe near the Fermi level were modified upon oxygen adsorption. By the detailed comparison of ARPES and DFT results of the oxygen adsorbed Fe surface, we have clarified the orbital-dependent p–d hybridization in the topmost and second Fe layers.Furthermore, the observed energy levels and Fermi wave numbers for the oxygen adsorbed Fe surface were deviated from the DFT calculations depending on the orbital characters and momentum directions, indicating an anisotropic interplay of the electron correlation and p–d hybridization effects in the surface region.
基金supported by the National Natural Science Foundation of China(Grant Nos.22176181,11874306,and 12174320)the Foundation of Science and Technology on Surface Physics and Chemistry Laboratory(Grant No.WDZC202101)the Natural Science Foundation of Chongqing,China(Grant No.cstc2021jcyj-msxmX0209)。
文摘The effect of strain on charge density wave(CDW)order inα-U is investigated within the framework of relativistic density-functional theory.The energetical stability ofα-U with CDW distortion is enhanced by the tensile strain along a and b axes,which is similar to the case of negative pressure and normal.However,the tensile strain along c axis suppresses the energetical stability of CDW phase.This abnormal effect could be understood from the emergence of a new onedimensional atomic chain along c axis inα-U.Furthermore,this effect is supported by the calculations of Fermi surface and phonon mode,in which the topological objects and the dynamical instability show opposite behaviors between strains along a/b and c axes.
基金National Natural Science Foundation of China(Grant Number:21763027)Innovation Team for Monitoring of Emerging Contaminants and Biomarkers(Grant Number:2021D14017)+2 种基金Xinjiang Regional Collaborative Innovation Project(Grant Number:2019E0223)Scientific Research Program of Colleges and Universities in Xinjiang(Grant Number:XJEDU2020Y029)“13th Five-Year”Plan for Key Discipline Physics Bidding Project of Xinjiang Normal University(Grant Number:17SDKD0602).
文摘Phosgene is highly toxic, and it plays a role in the depletion of the ozone layer. The ground state geometric structure and spectral characteristic of phosgene in various external electric fields were calculated via the density-functional theory (DFT) and time-dependent density-functional theory (TDDFT) with the B3LYP/6-31+G(d) basis set. With external electric field, the structure of phosgene changed significantly. With increasing electric field, the bond lengths of 1C-3Cl and 1C-4Cl increased;the total energy and energy gap initially increased and then decreased, whereas the dipole moment initially decreased and then increased. Most of the IR vibrational frequencies were redshifted. The wavelength of the singlet excited state increased, reflecting a red shift, and the oscillator strengths of most transitions belonged to forbidden transitions. These results are of great significance for studying the dissociation of phosgene in external electric field.
