We report a first-principles calculation to investigate the structural instability of rutile TiO2. The high pressure structural parameters are well reproduced. The calculated phonon disper-sion curves agree with exper...We report a first-principles calculation to investigate the structural instability of rutile TiO2. The high pressure structural parameters are well reproduced. The calculated phonon disper-sion curves agree with experiments at zero pressure. Under compression, we capture a large softening around Γ point, which indicates the structural instability. From the high pressure elastic constants, we find that the rutile TiO2 is unstable when the applied pressure is larger than 17.7 GPa. Within the quasi-harmonic approximation, the thermal equation of state, thermal expansion oefficient, bulk modulus, and entropy are well reproduced. The thermal properties confirm the available experimental data and are extended to a wider pressure and temperature range.展开更多
The phonon and thermodynamics properties of face-centered cubic CaF2 at high pressure and high temperature are investigated by using the shell model interatomic pair potential within General Utility Lattice Program （...The phonon and thermodynamics properties of face-centered cubic CaF2 at high pressure and high temperature are investigated by using the shell model interatomic pair potential within General Utility Lattice Program （GULP）. The phonon dispersion curves and the corresponding density of state （PDOS） in this work are consistent with the experimental data and other theoretical results. The transverse optical （TO） and longitudinal optical （LO） mode splitting as well as heat capacity at constant volume Cv and entropy S versus pressure and temperature are also obtained.展开更多
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.11247316, No.11247317, and No.11304408）, the Science and Technology Research Project of Chongqing Education Committee （No.K J120613 and No.K J130607）, and the Natural Science Foundation of Chongqing City （No.cstc2012jjA50019 and No.cstc2013jcyjA073a）.
文摘We report a first-principles calculation to investigate the structural instability of rutile TiO2. The high pressure structural parameters are well reproduced. The calculated phonon disper-sion curves agree with experiments at zero pressure. Under compression, we capture a large softening around Γ point, which indicates the structural instability. From the high pressure elastic constants, we find that the rutile TiO2 is unstable when the applied pressure is larger than 17.7 GPa. Within the quasi-harmonic approximation, the thermal equation of state, thermal expansion oefficient, bulk modulus, and entropy are well reproduced. The thermal properties confirm the available experimental data and are extended to a wider pressure and temperature range.
基金supported by the National Natural Science Foundation of China under Grant No.10576020
文摘The phonon and thermodynamics properties of face-centered cubic CaF2 at high pressure and high temperature are investigated by using the shell model interatomic pair potential within General Utility Lattice Program （GULP）. The phonon dispersion curves and the corresponding density of state （PDOS） in this work are consistent with the experimental data and other theoretical results. The transverse optical （TO） and longitudinal optical （LO） mode splitting as well as heat capacity at constant volume Cv and entropy S versus pressure and temperature are also obtained.
