There are five most widely used contact angle schemes in the pseudopotential lattice Boltzmann(LB)model for simulating the wetting phenomenon:The pseudopotential-based scheme(PB scheme),the improved virtualdensity sch...There are five most widely used contact angle schemes in the pseudopotential lattice Boltzmann(LB)model for simulating the wetting phenomenon:The pseudopotential-based scheme(PB scheme),the improved virtualdensity scheme(IVD scheme),the modified pseudopotential-based scheme with a ghost fluid layer constructed by using the fluid layer density above the wall(MPB-C scheme),the modified pseudopotential-based scheme with a ghost fluid layer constructed by using the weighted average density of surrounding fluid nodes(MPB-W scheme)and the geometric formulation scheme(GF scheme).But the numerical stability and accuracy of the schemes for wetting simulation remain unclear in the past.In this paper,the numerical stability and accuracy of these schemes are clarified for the first time,by applying the five widely used contact angle schemes to simulate a two-dimensional(2D)sessile droplet on wall and capillary imbibition in a 2D channel as the examples of static wetting and dynamic wetting simulations respectively.(i)It is shown that the simulated contact angles by the GF scheme are consistent at different density ratios for the same prescribed contact angle,but the simulated contact angles by the PB scheme,IVD scheme,MPB-C scheme and MPB-W scheme change with density ratios for the same fluid-solid interaction strength.The PB scheme is found to be the most unstable scheme for simulating static wetting at increased density ratios.(ii)Although the spurious velocity increases with the increased liquid/vapor density ratio for all the contact angle schemes,the magnitude of the spurious velocity in the PB scheme,IVD scheme and GF scheme are smaller than that in the MPB-C scheme and MPB-W scheme.(iii)The fluid density variation near the wall in the PB scheme is the most significant,and the variation can be diminished in the IVD scheme,MPB-C scheme andMPBWscheme.The variation totally disappeared in the GF scheme.(iv)For the simulation of capillary imbibition,the MPB-C scheme,MPB-Wscheme and GF scheme simulate the dynamics of the liquid-vapor interface well,with the GF scheme being the most accurate.The accuracy of the IVD scheme is low at a small contact angle(44 degrees)but gets high at a large contact angle(60 degrees).However,the PB scheme is the most inaccurate in simulating the dynamics of the liquid-vapor interface.As a whole,it is most suggested to apply the GF scheme to simulate static wetting or dynamic wetting,while it is the least suggested to use the PB scheme to simulate static wetting or dynamic wetting.展开更多
The dynamics of the cavitation bubble collapse is a fundamental issue for the bubble collapse application and prevention. In the present work, the modified forcing scheme for the pseudopotential multi-relaxation-time ...The dynamics of the cavitation bubble collapse is a fundamental issue for the bubble collapse application and prevention. In the present work, the modified forcing scheme for the pseudopotential multi-relaxation-time lattice Boltzmann model developed by Li Q et al. [ Li Q, Luo K H and Li X J 2013 Phys. Rev. E 87 053301] is adopted to develop a cavitation bubble collapse model. In the respects of coexistence curves and Laplace law verification, the improved pseudopotential multi-relaxation-time lattice Boltzmann model is investigated. It is found that the thermodynamic consistency and surface tension are independent of kinematic viscosity. By homogeneous and heterogeneous cavitation simulation, the ability of the present model to describe the cavitation bubble development as well as the cavitation inception is verified. The bubble collapse between two parallel walls is simulated. The dynamic process of a collapsing bubble is consistent with the results from experiments and simulations by other numerical methods. It is demonstrated that the present pseudopotential multirelaxation-time lattice Boltzmann model is applicable and efficient, and the lattice Boltzmann method is an alternative tool for collapsing bubble modeling.展开更多
The interaction between cavitation bubble and solid surface is a fundamental topic which is deeply concerned for the utilization or avoidance of cavitation effect.The complexity of this topic is that the cavitation bu...The interaction between cavitation bubble and solid surface is a fundamental topic which is deeply concerned for the utilization or avoidance of cavitation effect.The complexity of this topic is that the cavitation bubble collapse includes many extreme physical phenomena and variability of different solid surface properties.In the present work,the cavitation bubble collapse in hydrophobic concave is studied using the pseudopotential multi-relaxation-time lattice Boltzmann model(MRT-LB).The model is modified by involving the piecewise linear equation of state and improved forcing scheme.The fluid-solid interaction in the model is employed to adjust the wettability of solid surface.Moreover,the validity of the model is verified by comparison with experimental results and grid-independence verification.Finally,the cavitation bubble collapse in a hydrophobic concave is studied by investigating density field,pressure field,collapse time,and jet velocity.The superimposed effect of the surface hydrophobicity and concave geometry is analyzed and explained in the framework of the pseudopotential LBM.The study shows that the hydrophobic concave can enhance cavitation effect by decreasing cavitation threshold,accelerating collapse and increasing jet velocity.展开更多
Cavitation bubble collapse near rough solid wall is modeled by the multi-relaxation-time (MRT) pseudopotential lattice Boltzmann (LB) model. The modified forcing scheme, which can achieve LB model’s thermodynamic con...Cavitation bubble collapse near rough solid wall is modeled by the multi-relaxation-time (MRT) pseudopotential lattice Boltzmann (LB) model. The modified forcing scheme, which can achieve LB model’s thermodynamic consistency by tuning a parameter related with the particle interaction range, is adopted to achieve desired stability and density ratio. The bubble collapse near rough solid wall was simulated by the improved MRT pseudopotential LB model. The mechanism of bubble collapse is studied by investigating the bubble profiles, pressure field and velocity field evolution. The eroding effects of collapsing bubble are analyzed in details. It is found that the process and the effect of the interaction between bubble collapse and rough solid wall are affected seriously by the geometry of solid boundary. At the same time, it demonstrates that the MRT pseudopotential LB model is a potential tool for the investigation of the interaction mechanism between the collapsing bubble and complex geometry boundary.展开更多
The fragments such as TiCl<sub>2</sub> are encountered in the study of the reaction mechanism about organometallic complexes and clusters. It is of significanoce to study the metastables for the investigat...The fragments such as TiCl<sub>2</sub> are encountered in the study of the reaction mechanism about organometallic complexes and clusters. It is of significanoce to study the metastables for the investigation of the reaction mechanism and the synthesis of a new type of clusters and organometallic complexes. Hoffmann and his co-workers developed isolobal analogue theory and proved it by using EHMO and other qualitative methods. However, in展开更多
RgH (Rg represents the rare gases) molecules are different from the commonhydrides, becasue its ground state is repulsive, but its excited state is bound. So it isexpected to be used as the producer of laser, of which...RgH (Rg represents the rare gases) molecules are different from the commonhydrides, becasue its ground state is repulsive, but its excited state is bound. So it isexpected to be used as the producer of laser, of which the frequency can be展开更多
To directly incorporate the intermolecular interaction effects into the discrete unified gas-kinetic scheme(DUGKS)for simulations of multiphase fluid flow,we developed a pseudopotential-based DUGKS by coupling the pse...To directly incorporate the intermolecular interaction effects into the discrete unified gas-kinetic scheme(DUGKS)for simulations of multiphase fluid flow,we developed a pseudopotential-based DUGKS by coupling the pseudopotential model that mimics the intermolecular interaction into DUGKS.Due to the flux reconstruction procedure,additional terms that break the isotropic requirements of the pseudopotential model will be introduced.To eliminate the influences of nonisotropic terms,the expression of equilibrium distribution functions is reformulated in a moment-based form.With the isotropy-preserving parameter appropriately tuned,the nonisotropic effects can be properly canceled out.The fundamental capabilities are validated by the flat interface test and the quiescent droplet test.It has been proved that the proposed pseudopotential-based DUGKS managed to produce and maintain isotropic interfaces.The isotropy-preserving property of pseudopotential-based DUGKS in transient conditions is further confirmed by the spinodal decomposition.Stability superiority of the pseudopotential-based DUGKS over the lattice Boltzmann method is also demonstrated by predicting the coexistence densities complying with the van der Waals equation of state.By directly incorporating the intermolecular interactions,the pseudopotential-based DUGKS offers a mesoscopic perspective of understanding multiphase behaviors,which could help gain fresh insights into multiphase fluid flow.展开更多
We have studied the structural and atomic transport properties of liquid f-shell Yb in the temperature range 1123 K–1473 K. Pair interactions between atoms are derived using a local pseudopotential. The potential par...We have studied the structural and atomic transport properties of liquid f-shell Yb in the temperature range 1123 K–1473 K. Pair interactions between atoms are derived using a local pseudopotential. The potential parameters are fitted to the phonon dispersion curve at room temperature. The local pseudopotential used in the present study is computationally more efficient with only three parameters, and it is found to be transferable to the liquid phase without changing the parameters.Since the various computed properties agree with reported theoretical and experimental findings, the adopted fitting scheme is justified. As a significant outcome of the study, we find that(i) the melting in Yb is governed by the Lindemann's law,(ii)the mass transport mechanism obeys the Arrhenius law,(iii) the role of the three-particle correlation function in deriving the velocity autocorrelation function is small,(iv) the mean-square atomic displacement is more sensitive to the choice of interaction potential than the other bulk properties, and(v) liquid Yb does not show liquid–liquid phase transition within the studied temperature range. Further, due to the good description of the structural and mass transport properties, we propose that Yb remains divalent at reduced density.展开更多
Within the framework of the density functional theory and the pseudopotential method,the electronic structure calculations of the“metal-Si(100)”systems with Li,Be and Al as metal coverings of one to four monolayers(...Within the framework of the density functional theory and the pseudopotential method,the electronic structure calculations of the“metal-Si(100)”systems with Li,Be and Al as metal coverings of one to four monolayers(ML)thickness,were carried out.Calculations showed that band gaps of 1.02 eV,0.98 eV and 0.5 eV,respectively,appear in the densities of electronic states when the thickness of Li,Be and Al coverings is one ML.These gaps disappear with increasing thickness of the metal layers:first in the Li-Si system(for two ML),then in the Al-Si system(for three ML)and then in the Be-Si system(for four ML).This behavior of the band gap can be explained by the passivation of the substrate surface states and the peculiarities of the electronic structure of the adsorbed metals.In common the results can be interpreted as describing the possibility of the formation of a two-dimensional silicide with semiconducting properties in Li-Si(100),Be-Si(100)and Al-Si(100)systems.展开更多
Detailed theoretical investigations into asphericity in the Fermi surface (FS) and Fermi energy (FE) ofNa1_xKx, Na1_xRbx, and Na1_xCsx binary solid solutions are carried out for the first time. The alloying behavior o...Detailed theoretical investigations into asphericity in the Fermi surface (FS) and Fermi energy (FE) ofNa1_xKx, Na1_xRbx, and Na1_xCsx binary solid solutions are carried out for the first time. The alloying behavior ofthe K, Rb, and Cs with the Na generates the Fermi surface distortion (FSD) of bce simple metals. The FS of Na-K,Na-Rb, and Na-Cs solid solution is a distorted sphere with the largest deviation along [110]. We have found that theimpact of local-field correction function on FSD is maximun at [100] point and minimum at [111] point. The exchangeand correlation effect is found to suppress the value of FE.展开更多
The electronic states of“wurtzite”CdS nanoparticles and CdSe/CdS nanosystems with up to 80 pairs of Cd-Se or CdS atoms were calculated.The results for CdS particles were compared with the results obtained earlier fo...The electronic states of“wurtzite”CdS nanoparticles and CdSe/CdS nanosystems with up to 80 pairs of Cd-Se or CdS atoms were calculated.The results for CdS particles were compared with the results obtained earlier for CdSe particles of the same size and with published calculations of other authors.The calculated gap values in the range of 2.84 eV~3.78 eV are typical for CdS particles of studied sizes in accordance with results of published data.The CdSe/CdS nanosystems were considered as layered ones and as quantum dots.The layered CdSe/CdS systems with two-layer CdS coverings can be interpreted in terms of combinations of two semiconductors with different energy band gaps(2.6 eV and 3.3 eV),while analogous systems with single-layer CdS coverings do not demonstrate a two-gap electron structure.Simulation of a CdSe/CdS quantum dot shows that the single-layer CdS shell demonstrates a tendency for the formation of the electronic structure with two energy gaps:approximately of 2.5 eV and 3.0 eV.展开更多
The authors fulfilled calculations of the total energy and electronic states of Cd_(n)Se_(n) nanoparticle:“wurzite”,“sphalerite”and“rock-salt”types of the structure.It was shown that at n≤72 the“rock-salt”typ...The authors fulfilled calculations of the total energy and electronic states of Cd_(n)Se_(n) nanoparticle:“wurzite”,“sphalerite”and“rock-salt”types of the structure.It was shown that at n≤72 the“rock-salt”type is the most favorable energetically.However the extrapolation of the behavior of the energy per Cd-Se atomic pair shows that for n>130(corresponding to a size of about 2 nm),particles with a“wurtzite”structure can be more advantageous.Particles of the“wurtzite”and“rock-salt”types have an electronic structure with an energy gap.For particles with the“wurtzite”structure,the gap width decreases with increasing particle size:from 3.3 eV to 2.2 eV as the particle increases from 0.5 nm to 1.5 nm.For particles of the“rock-salt”type,the gap width grows slightly,remaining about 3 eV.“Sphalerite”-type particles have a metal-like electronic structure.展开更多
Based on experimental results that VH0.81/MgH2 interface was found during the process of mechanically milling MgH2+5at.%V nanocomposite, H atoms diffusion and adsorption properties of MgH2-V systems have been investig...Based on experimental results that VH0.81/MgH2 interface was found during the process of mechanically milling MgH2+5at.%V nanocomposite, H atoms diffusion and adsorption properties of MgH2-V systems have been investigated by using a first-principles plane-wave pseudopotential method based on the density functional theory. The results are as follows. When VH/MgH2 interface is formed due to V alloying MgH2 phase, the vacancy formed by H atoms near VH phase region is more stable than that without V alloying, while vacancy near MgH2 phase region is less stable than that without V alloying. During the process of H atoms diffusion after V alloying, the max migration barrier energy of H atoms in MgH2-V systems is reduced compared with that of MgH2 phase, which means that H atoms diffuse easily. When H diffuses into VH from MgH2 across VH/MgH2 interface, among three substitutions such as the replacement of H for V vacancy, or interstitial site or V atoms, the replacement of H for V vacancy has the strongest diffusion ability, next interstitial site, and finally V atoms site. As far as H adsorbed on different surfaces of VH phase is concerned, physical adsorption is carried out more easily than chemical adsorption, and the behavior of H atoms adsorbed on the surface near VH phase region can be found more easily than that near MgH2 phase region.展开更多
The molecular constants of selected diatomic lanthanide compounds (LaH, LaO, LaF, EuH, EuO, EuF, EuS, GdO, GdF, GdH, YbH, YbO, YbF, YbS, LuH, LuO and LuF) have been calculated by using relativistic small-core pseudopo...The molecular constants of selected diatomic lanthanide compounds (LaH, LaO, LaF, EuH, EuO, EuF, EuS, GdO, GdF, GdH, YbH, YbO, YbF, YbS, LuH, LuO and LuF) have been calculated by using relativistic small-core pseudopotentials and optimized (14s13p10d8f6g)/ [6s6p5d4f3g] valence basis sets. The results are in good agreement with available experimental data, with exception of YbO and LuF. The reasons for the discrepancies in case of YbO are due to a complicated mixing of configurations in the ground state, whereas in case of LuF the binding energy estimated by experimentalists appears to be too low.展开更多
The well recognized model potential is used to investigate the vibrational properties of four Fe-based binary glassy alloys viz.Fe_(90)Zr_(10),Fe_(80)B_(20),Fe_(83)B_(17) and Fe_(80)P_(20).The thermodynamic and elasti...The well recognized model potential is used to investigate the vibrational properties of four Fe-based binary glassy alloys viz.Fe_(90)Zr_(10),Fe_(80)B_(20),Fe_(83)B_(17) and Fe_(80)P_(20).The thermodynamic and elastic properties are also computed from the elastic limits of the phonon dispersion curves(PDC).Three theoretical approaches given by Hubbard-Beeby(HB),Takeno-Goda(TG)and Bhatia-Singh(BS)are used in the present study to compute the PDC.Six local field correction functions proposed by Hartree(H),Taylor(T),Ichimaru-Utsumi(IU),Farid et al.(F)and Sarkar et al.(S)and Sarkar et al.’s local field factor(SLFF)based excgange and correlation function are employed to see the effect of exchange and correlation in the aforesaid properties.展开更多
The well known model potential is used to investigate the vibrational properties of some Ni-based binary glassy alloys using three theoretical models.Different local field correction functions are employed to see the ...The well known model potential is used to investigate the vibrational properties of some Ni-based binary glassy alloys using three theoretical models.Different local field correction functions are employed to see the effect of exchange and correlation in the aforesaid properties and have been found successful.展开更多
The well recognized model potential is used to investigate the phonon properties for five glassy Copper alloys viz.Cu_(57)Zr_(43),Cu_(60)W_(40),Cu_(33)Y_(67),Cu_(43)Ti_(57) and Cu_(66)Ti_(34).The thermodynamic and ela...The well recognized model potential is used to investigate the phonon properties for five glassy Copper alloys viz.Cu_(57)Zr_(43),Cu_(60)W_(40),Cu_(33)Y_(67),Cu_(43)Ti_(57) and Cu_(66)Ti_(34).The thermodynamic and elastic properties are also computed from the elastic limits of the phonon dispersion curves(PDC).Three theoretical approaches given by Hubbard-Beeby(HB),Takeno-Goda(TG)and Bhatia-Singh(BS)are used in the present study to compute the PDC.Five local field correction functions proposed by Hartree(H),Taylor(T),Ichimaru-Utsumi(IU),Farid et al.(F)and Sarkar et al.(S)are employed to see the effect of exchange and correlation in the aforesaid properties.展开更多
An extension of the standard Shan-Chen model for non ideal-fluids,catering for mid-range,soft-core and hard-core repulsion,is investigated.It is shown that the inclusion of such mid-range interactions does not yield a...An extension of the standard Shan-Chen model for non ideal-fluids,catering for mid-range,soft-core and hard-core repulsion,is investigated.It is shown that the inclusion of such mid-range interactions does not yield any visible enhancement of the density jump across the dense and light phases.Such an enhancement can however be obtained by tuning the exponents of the effective interaction.The results also indicate that the inclusion of soft-core repulsion can prevent the coalescence of neighborhood bubbles,thereby opening the possibility of tailoring the size of multi-droplet configurations,such as sprays and related phase-separating fluids.展开更多
基金sponsored by the National Natural Science Foundation of China under Grant No.52206101Shanghai Sailing Program under Grant No.20YF1431200the Experiments for Space Exploration Program and the Qian Xuesen Laboratory,China Academy of Space Technology under Grant No.TKTSPY-2020-01-01.
文摘There are five most widely used contact angle schemes in the pseudopotential lattice Boltzmann(LB)model for simulating the wetting phenomenon:The pseudopotential-based scheme(PB scheme),the improved virtualdensity scheme(IVD scheme),the modified pseudopotential-based scheme with a ghost fluid layer constructed by using the fluid layer density above the wall(MPB-C scheme),the modified pseudopotential-based scheme with a ghost fluid layer constructed by using the weighted average density of surrounding fluid nodes(MPB-W scheme)and the geometric formulation scheme(GF scheme).But the numerical stability and accuracy of the schemes for wetting simulation remain unclear in the past.In this paper,the numerical stability and accuracy of these schemes are clarified for the first time,by applying the five widely used contact angle schemes to simulate a two-dimensional(2D)sessile droplet on wall and capillary imbibition in a 2D channel as the examples of static wetting and dynamic wetting simulations respectively.(i)It is shown that the simulated contact angles by the GF scheme are consistent at different density ratios for the same prescribed contact angle,but the simulated contact angles by the PB scheme,IVD scheme,MPB-C scheme and MPB-W scheme change with density ratios for the same fluid-solid interaction strength.The PB scheme is found to be the most unstable scheme for simulating static wetting at increased density ratios.(ii)Although the spurious velocity increases with the increased liquid/vapor density ratio for all the contact angle schemes,the magnitude of the spurious velocity in the PB scheme,IVD scheme and GF scheme are smaller than that in the MPB-C scheme and MPB-W scheme.(iii)The fluid density variation near the wall in the PB scheme is the most significant,and the variation can be diminished in the IVD scheme,MPB-C scheme andMPBWscheme.The variation totally disappeared in the GF scheme.(iv)For the simulation of capillary imbibition,the MPB-C scheme,MPB-Wscheme and GF scheme simulate the dynamics of the liquid-vapor interface well,with the GF scheme being the most accurate.The accuracy of the IVD scheme is low at a small contact angle(44 degrees)but gets high at a large contact angle(60 degrees).However,the PB scheme is the most inaccurate in simulating the dynamics of the liquid-vapor interface.As a whole,it is most suggested to apply the GF scheme to simulate static wetting or dynamic wetting,while it is the least suggested to use the PB scheme to simulate static wetting or dynamic wetting.
基金supported by the National Natural Science Foundation of China(Grant Nos.11274092 and 1140040119)the Natural Science Foundation of Jiangsu Province,China(Grant No.SBK2014043338)
文摘The dynamics of the cavitation bubble collapse is a fundamental issue for the bubble collapse application and prevention. In the present work, the modified forcing scheme for the pseudopotential multi-relaxation-time lattice Boltzmann model developed by Li Q et al. [ Li Q, Luo K H and Li X J 2013 Phys. Rev. E 87 053301] is adopted to develop a cavitation bubble collapse model. In the respects of coexistence curves and Laplace law verification, the improved pseudopotential multi-relaxation-time lattice Boltzmann model is investigated. It is found that the thermodynamic consistency and surface tension are independent of kinematic viscosity. By homogeneous and heterogeneous cavitation simulation, the ability of the present model to describe the cavitation bubble development as well as the cavitation inception is verified. The bubble collapse between two parallel walls is simulated. The dynamic process of a collapsing bubble is consistent with the results from experiments and simulations by other numerical methods. It is demonstrated that the present pseudopotential multirelaxation-time lattice Boltzmann model is applicable and efficient, and the lattice Boltzmann method is an alternative tool for collapsing bubble modeling.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11874140 and 11574072)the Fund from the State Key Laboratory of Acoustics,Chinese Academy of Sciences(Grant No.SKLA201913)+1 种基金the National Key Research and Development Program of China(Grant No.2016YFC0401600)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant Nos.2018B741X14 and KYCX180552)。
文摘The interaction between cavitation bubble and solid surface is a fundamental topic which is deeply concerned for the utilization or avoidance of cavitation effect.The complexity of this topic is that the cavitation bubble collapse includes many extreme physical phenomena and variability of different solid surface properties.In the present work,the cavitation bubble collapse in hydrophobic concave is studied using the pseudopotential multi-relaxation-time lattice Boltzmann model(MRT-LB).The model is modified by involving the piecewise linear equation of state and improved forcing scheme.The fluid-solid interaction in the model is employed to adjust the wettability of solid surface.Moreover,the validity of the model is verified by comparison with experimental results and grid-independence verification.Finally,the cavitation bubble collapse in a hydrophobic concave is studied by investigating density field,pressure field,collapse time,and jet velocity.The superimposed effect of the surface hydrophobicity and concave geometry is analyzed and explained in the framework of the pseudopotential LBM.The study shows that the hydrophobic concave can enhance cavitation effect by decreasing cavitation threshold,accelerating collapse and increasing jet velocity.
文摘Cavitation bubble collapse near rough solid wall is modeled by the multi-relaxation-time (MRT) pseudopotential lattice Boltzmann (LB) model. The modified forcing scheme, which can achieve LB model’s thermodynamic consistency by tuning a parameter related with the particle interaction range, is adopted to achieve desired stability and density ratio. The bubble collapse near rough solid wall was simulated by the improved MRT pseudopotential LB model. The mechanism of bubble collapse is studied by investigating the bubble profiles, pressure field and velocity field evolution. The eroding effects of collapsing bubble are analyzed in details. It is found that the process and the effect of the interaction between bubble collapse and rough solid wall are affected seriously by the geometry of solid boundary. At the same time, it demonstrates that the MRT pseudopotential LB model is a potential tool for the investigation of the interaction mechanism between the collapsing bubble and complex geometry boundary.
基金Project supported by the National Natural Science Foundation of China
文摘The fragments such as TiCl<sub>2</sub> are encountered in the study of the reaction mechanism about organometallic complexes and clusters. It is of significanoce to study the metastables for the investigation of the reaction mechanism and the synthesis of a new type of clusters and organometallic complexes. Hoffmann and his co-workers developed isolobal analogue theory and proved it by using EHMO and other qualitative methods. However, in
基金Project supported by the National Natural Science Foundation of China.
文摘RgH (Rg represents the rare gases) molecules are different from the commonhydrides, becasue its ground state is repulsive, but its excited state is bound. So it isexpected to be used as the producer of laser, of which the frequency can be
基金National Numerical Wind Tunnel Project,the National Natural Science Foundation of China(No.11902266,11902264,12072283)111 Project of China(B17037).
文摘To directly incorporate the intermolecular interaction effects into the discrete unified gas-kinetic scheme(DUGKS)for simulations of multiphase fluid flow,we developed a pseudopotential-based DUGKS by coupling the pseudopotential model that mimics the intermolecular interaction into DUGKS.Due to the flux reconstruction procedure,additional terms that break the isotropic requirements of the pseudopotential model will be introduced.To eliminate the influences of nonisotropic terms,the expression of equilibrium distribution functions is reformulated in a moment-based form.With the isotropy-preserving parameter appropriately tuned,the nonisotropic effects can be properly canceled out.The fundamental capabilities are validated by the flat interface test and the quiescent droplet test.It has been proved that the proposed pseudopotential-based DUGKS managed to produce and maintain isotropic interfaces.The isotropy-preserving property of pseudopotential-based DUGKS in transient conditions is further confirmed by the spinodal decomposition.Stability superiority of the pseudopotential-based DUGKS over the lattice Boltzmann method is also demonstrated by predicting the coexistence densities complying with the van der Waals equation of state.By directly incorporating the intermolecular interactions,the pseudopotential-based DUGKS offers a mesoscopic perspective of understanding multiphase behaviors,which could help gain fresh insights into multiphase fluid flow.
文摘We have studied the structural and atomic transport properties of liquid f-shell Yb in the temperature range 1123 K–1473 K. Pair interactions between atoms are derived using a local pseudopotential. The potential parameters are fitted to the phonon dispersion curve at room temperature. The local pseudopotential used in the present study is computationally more efficient with only three parameters, and it is found to be transferable to the liquid phase without changing the parameters.Since the various computed properties agree with reported theoretical and experimental findings, the adopted fitting scheme is justified. As a significant outcome of the study, we find that(i) the melting in Yb is governed by the Lindemann's law,(ii)the mass transport mechanism obeys the Arrhenius law,(iii) the role of the three-particle correlation function in deriving the velocity autocorrelation function is small,(iv) the mean-square atomic displacement is more sensitive to the choice of interaction potential than the other bulk properties, and(v) liquid Yb does not show liquid–liquid phase transition within the studied temperature range. Further, due to the good description of the structural and mass transport properties, we propose that Yb remains divalent at reduced density.
文摘Within the framework of the density functional theory and the pseudopotential method,the electronic structure calculations of the“metal-Si(100)”systems with Li,Be and Al as metal coverings of one to four monolayers(ML)thickness,were carried out.Calculations showed that band gaps of 1.02 eV,0.98 eV and 0.5 eV,respectively,appear in the densities of electronic states when the thickness of Li,Be and Al coverings is one ML.These gaps disappear with increasing thickness of the metal layers:first in the Li-Si system(for two ML),then in the Al-Si system(for three ML)and then in the Be-Si system(for four ML).This behavior of the band gap can be explained by the passivation of the substrate surface states and the peculiarities of the electronic structure of the adsorbed metals.In common the results can be interpreted as describing the possibility of the formation of a two-dimensional silicide with semiconducting properties in Li-Si(100),Be-Si(100)and Al-Si(100)systems.
文摘Detailed theoretical investigations into asphericity in the Fermi surface (FS) and Fermi energy (FE) ofNa1_xKx, Na1_xRbx, and Na1_xCsx binary solid solutions are carried out for the first time. The alloying behavior ofthe K, Rb, and Cs with the Na generates the Fermi surface distortion (FSD) of bce simple metals. The FS of Na-K,Na-Rb, and Na-Cs solid solution is a distorted sphere with the largest deviation along [110]. We have found that theimpact of local-field correction function on FSD is maximun at [100] point and minimum at [111] point. The exchangeand correlation effect is found to suppress the value of FE.
文摘The electronic states of“wurtzite”CdS nanoparticles and CdSe/CdS nanosystems with up to 80 pairs of Cd-Se or CdS atoms were calculated.The results for CdS particles were compared with the results obtained earlier for CdSe particles of the same size and with published calculations of other authors.The calculated gap values in the range of 2.84 eV~3.78 eV are typical for CdS particles of studied sizes in accordance with results of published data.The CdSe/CdS nanosystems were considered as layered ones and as quantum dots.The layered CdSe/CdS systems with two-layer CdS coverings can be interpreted in terms of combinations of two semiconductors with different energy band gaps(2.6 eV and 3.3 eV),while analogous systems with single-layer CdS coverings do not demonstrate a two-gap electron structure.Simulation of a CdSe/CdS quantum dot shows that the single-layer CdS shell demonstrates a tendency for the formation of the electronic structure with two energy gaps:approximately of 2.5 eV and 3.0 eV.
文摘The authors fulfilled calculations of the total energy and electronic states of Cd_(n)Se_(n) nanoparticle:“wurzite”,“sphalerite”and“rock-salt”types of the structure.It was shown that at n≤72 the“rock-salt”type is the most favorable energetically.However the extrapolation of the behavior of the energy per Cd-Se atomic pair shows that for n>130(corresponding to a size of about 2 nm),particles with a“wurtzite”structure can be more advantageous.Particles of the“wurtzite”and“rock-salt”types have an electronic structure with an energy gap.For particles with the“wurtzite”structure,the gap width decreases with increasing particle size:from 3.3 eV to 2.2 eV as the particle increases from 0.5 nm to 1.5 nm.For particles of the“rock-salt”type,the gap width grows slightly,remaining about 3 eV.“Sphalerite”-type particles have a metal-like electronic structure.
基金the Ministry of Science and Technology of China (Grant No. 2006CB605104)the National Natural Science Foundation of China (Grant No. 50771044)
文摘Based on experimental results that VH0.81/MgH2 interface was found during the process of mechanically milling MgH2+5at.%V nanocomposite, H atoms diffusion and adsorption properties of MgH2-V systems have been investigated by using a first-principles plane-wave pseudopotential method based on the density functional theory. The results are as follows. When VH/MgH2 interface is formed due to V alloying MgH2 phase, the vacancy formed by H atoms near VH phase region is more stable than that without V alloying, while vacancy near MgH2 phase region is less stable than that without V alloying. During the process of H atoms diffusion after V alloying, the max migration barrier energy of H atoms in MgH2-V systems is reduced compared with that of MgH2 phase, which means that H atoms diffuse easily. When H diffuses into VH from MgH2 across VH/MgH2 interface, among three substitutions such as the replacement of H for V vacancy, or interstitial site or V atoms, the replacement of H for V vacancy has the strongest diffusion ability, next interstitial site, and finally V atoms site. As far as H adsorbed on different surfaces of VH phase is concerned, physical adsorption is carried out more easily than chemical adsorption, and the behavior of H atoms adsorbed on the surface near VH phase region can be found more easily than that near MgH2 phase region.
文摘The molecular constants of selected diatomic lanthanide compounds (LaH, LaO, LaF, EuH, EuO, EuF, EuS, GdO, GdF, GdH, YbH, YbO, YbF, YbS, LuH, LuO and LuF) have been calculated by using relativistic small-core pseudopotentials and optimized (14s13p10d8f6g)/ [6s6p5d4f3g] valence basis sets. The results are in good agreement with available experimental data, with exception of YbO and LuF. The reasons for the discrepancies in case of YbO are due to a complicated mixing of configurations in the ground state, whereas in case of LuF the binding energy estimated by experimentalists appears to be too low.
文摘The well recognized model potential is used to investigate the vibrational properties of four Fe-based binary glassy alloys viz.Fe_(90)Zr_(10),Fe_(80)B_(20),Fe_(83)B_(17) and Fe_(80)P_(20).The thermodynamic and elastic properties are also computed from the elastic limits of the phonon dispersion curves(PDC).Three theoretical approaches given by Hubbard-Beeby(HB),Takeno-Goda(TG)and Bhatia-Singh(BS)are used in the present study to compute the PDC.Six local field correction functions proposed by Hartree(H),Taylor(T),Ichimaru-Utsumi(IU),Farid et al.(F)and Sarkar et al.(S)and Sarkar et al.’s local field factor(SLFF)based excgange and correlation function are employed to see the effect of exchange and correlation in the aforesaid properties.
文摘The well known model potential is used to investigate the vibrational properties of some Ni-based binary glassy alloys using three theoretical models.Different local field correction functions are employed to see the effect of exchange and correlation in the aforesaid properties and have been found successful.
文摘The well recognized model potential is used to investigate the phonon properties for five glassy Copper alloys viz.Cu_(57)Zr_(43),Cu_(60)W_(40),Cu_(33)Y_(67),Cu_(43)Ti_(57) and Cu_(66)Ti_(34).The thermodynamic and elastic properties are also computed from the elastic limits of the phonon dispersion curves(PDC).Three theoretical approaches given by Hubbard-Beeby(HB),Takeno-Goda(TG)and Bhatia-Singh(BS)are used in the present study to compute the PDC.Five local field correction functions proposed by Hartree(H),Taylor(T),Ichimaru-Utsumi(IU),Farid et al.(F)and Sarkar et al.(S)are employed to see the effect of exchange and correlation in the aforesaid properties.
文摘An extension of the standard Shan-Chen model for non ideal-fluids,catering for mid-range,soft-core and hard-core repulsion,is investigated.It is shown that the inclusion of such mid-range interactions does not yield any visible enhancement of the density jump across the dense and light phases.Such an enhancement can however be obtained by tuning the exponents of the effective interaction.The results also indicate that the inclusion of soft-core repulsion can prevent the coalescence of neighborhood bubbles,thereby opening the possibility of tailoring the size of multi-droplet configurations,such as sprays and related phase-separating fluids.
