Entropy driven stabilization of energetically unstable crystal structures explained from first principles theory.
Entropy driven stabilization of energetically unstable crystal structures explained from first principles theory.
复制标题
DOI：
10.1103/physrevlett.100.095901
复制
发表时间：
2008-03
影响因子：
8.6
通讯作者：
P. Souvatzis;O. Eriksson;M. Katsnelson;S. Rudin
中科院分区：
文献类型：
--
作者：
P. Souvatzis;O. Eriksson;M. Katsnelson;S. Rudin
传统的晶体热力学计算方法是用谐波声子谱来计算的，因此，在晶体结构在谐波近似下不稳定的情况下，如体心立方（bcc）晶体结构，当它作为许多金属的高温相出现时，就不能正常工作。为了解决这一问题，开发了一种从第一性原理计算温度相关声子谱的自一致方法。该方法结合了玻恩原子间自一致声子方法的概念和超级单体中精确原子间作用力的第一性原理计算。以Ti、Zr和Hf的高温bcc相为例，对该方法进行了测试，结果表明，该方法能较好地再现观测到的高温声子频率。
Conventional methods to calculate the thermodynamics of crystals evaluate the harmonic phonon spectra and therefore do not work in frequent and important situations where the crystal structure is unstable in the harmonic approximation, such as the body-centered cubic (bcc) crystal structure when it appears as a high-temperature phase of many metals. A method for calculating temperature dependent phonon spectra self-consistently from first principles has been developed to address this issue. The method combines concepts from Born's interatomic self-consistent phonon approach with first principles calculations of accurate interatomic forces in a supercell. The method has been tested on the high-temperature bcc phase of Ti, Zr, and Hf, as representative examples, and is found to reproduce the observed high-temperature phonon frequencies with good accuracy.