第一性原理对金的高压相变和零温物态方程的计算

First-principle calculations of phase transitions and equation of state at T=0-K for gold

在密度泛函理论下,用缀加平面波加局域轨道方法,分别采用广义梯度近似(GGA)和局域密度近似(LDA)对金的面心立方晶格结构(fcc)、体心立方晶格结构(bcc)和六角密堆积结构(hcp)的结构能量进行了计算.在GGA下,计算得出fcc向hcp和hcp向bcc的相变分别发生在380GPa和1250GPa;而LDA下相变分别发生在490GPa和790GPa.当计算压强达到2TPa时,bcc在这两种近似下仍然保持稳定的结构.根据不同体积下不同结构的电子态密度的特征,对发生相变的物理原因进行了定性的分析,在此基础上得到了金的零温状态方程.

In the framework of density functional theory, the static-lattice equation of state and structural phase stability of gold have been calculated to 2 TPa by using the augmented plane wave plus local orbital method with two distinct exchange-correlation energies; corresponding to the generalized gradient approximation （GGA） and the local density approximation （LDA）, respectively. The fcc structure is predicted to be the most stable phase at zero pressure, transforming to the hcp structure at 380 GPa （GGA） or 490 GPa （LDA）, and the hcp structure transforming to the bec structure at 1250 GPa （GGA） or 790 GPa （LDA）, which then remains stable to up 2 TPa. The possible reasons of the phase-transition are analyzed from the electronic density of state at the different phases and volumes. The equation of state at T = 0 K is also given based on the calculated structural result.