高压下FCC相金属氢结构稳定性和非谐效应的理论研究

Structural Stability and Anharmonic Effect of Metallic Hydrogen FCC Phase Under High Pressures

利用第一性原理分子动力学方法研究金属氢体系的非简谐效应,给出金属氢的声子谱,讨论金属氢声子谱的温度效应。计算得到氢的同位素氕、氘和氚的FCC相在非零温下的声子谱,不同温度下的声子谱对比发现零温下3.6 TPa为热力学稳定的临界压强点,而有限温度下(100 K)临界压强点降到2.8 TPa,非简谐效应显著地改变了体系的结构稳定性和声子振动性质。

First principles molecular dynamics calculation is used to study anharmonic effect of metallic hydrogen system.Lattice vibrations of metallic hydrogen are given,and temperature effect of phonon spectrum of metallic hydrogen is discussed.Phonon dispersions of FCC phases of protium,deuterium and tritium at non-zero temperature were given.Comparing phonon dispersions at different temperatures,we found that 3.6 TPa is the critical pressure of thermodynamic stability at zero temperature,while the critical pressure dropped to 2.8 TPa at a finite temperature(100 K).Anharmonic effect changes significantly stability and phonon dispersions of the system.