Thermodynamic properties of wadsleyite with anharmonic effect  

作　　者：Zhongqing Wu 

机构地区：[1]Laboratory of Seismology and Physics of Earth’s Interior,School of Earth and Space Sciences,University of Science and Technology of China [2]Mengcheng National Geophysical Observatory,University of Science and Technology of China

出　　处：《Earthquake Science》2015年第1期11-16,共6页地震学报（英文版）

基　　金：supported by State Key Development Program of Basic Research of China (2014CB845905);the Natural Science Foundation of China (41274087)

摘　　要：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.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.

关 键 词：First principles FORSTERITE THERMALEXPANSION GriJnisen parameter 

分 类 号：P315[天文地球—地震学]