The thermodynamic properties of crystals can be routinely calculated by density functional theory calculations combining with quasi-harmonic approximation. Based on the method developed recently by Wu and Wentzcovitch...The thermodynamic properties of crystals can be routinely calculated by density functional theory calculations combining with quasi-harmonic approximation. Based on the method developed recently by Wu and Wentzcovitch （Phys Rev B 79：104304, 2009） and Wu （Phys Rev B 81：172301, 2010）, we are able to further ab initio include anharmonic effect on thermodynamic properties of crystals by one additional canonical ensemble with numbers of particle, volume and temperature fixed （NVT） molecular dynamic simulations. Our study indicates that phonon-phonon interaction causes the renormalized phonon frequencies of wadsleyite decrease with temperature. This is consistent with the Raman experimental observation. The anharmonic free energy of wadsleyite is negative and its heat capacity at constant pressure can exceed the Dulong-Petit limit at high temperature. The anharmonicity still significantly affects thermodynamic properties of wadsleyite at pressure and temperature con- ditions correspond to the transition zone.展开更多
基金supported by State Key Development Program of Basic Research of China (2014CB845905)the Natural Science Foundation of China (41274087)
文摘The thermodynamic properties of crystals can be routinely calculated by density functional theory calculations combining with quasi-harmonic approximation. Based on the method developed recently by Wu and Wentzcovitch （Phys Rev B 79：104304, 2009） and Wu （Phys Rev B 81：172301, 2010）, we are able to further ab initio include anharmonic effect on thermodynamic properties of crystals by one additional canonical ensemble with numbers of particle, volume and temperature fixed （NVT） molecular dynamic simulations. Our study indicates that phonon-phonon interaction causes the renormalized phonon frequencies of wadsleyite decrease with temperature. This is consistent with the Raman experimental observation. The anharmonic free energy of wadsleyite is negative and its heat capacity at constant pressure can exceed the Dulong-Petit limit at high temperature. The anharmonicity still significantly affects thermodynamic properties of wadsleyite at pressure and temperature con- ditions correspond to the transition zone.
