非谐效应对过渡金属热力学性质和相变影响的理论研究

The research on the equation of state and phase transition of transition metals under high temperature and pressure are very important in the field of earth and planetary physics, physical weapons, spacecraft safety technology. The accurate solution of the equation of state is dependent on the exact calculation of the thermodynamical properties of materials. The theoretical values gradually deviate from the experimental data with the increase of temperature. In the present work, by fully consider the high temperature anharmonic effect, we utilize the recently developed upsampled thermodynamic integration using Langevin dynamics (UP-TILD) method to accurately calculate the free energy of transition metals Pt and Mo. Subsequently, the derivative values involved in the thermodynamical properties, Gibbs energy and phonon dispersion relations can be obtained by using the fundamental laws of thermodynamics. Therefore, following the information obtained, we analyze the anharmonic effect on equation of state, thermodynamic properties and phase transformation for Pt and Mo under high temperature and temperature. The project will help to understand the physical mechanism of the anharmonic effect emerged in transition metals and support the accurate calculation method of the equation of state, and also provide further understanding and study of the transition metal structural, physical and chemical properties at high temperature and pressure.

高温高压下过渡金属的物态方程和相变研究，在地球和行星物理、武器物理、航天飞行器安全防护技术等研究领域有着重要的应用背景。材料物态方程的准确求解基于其热力学性质的精确计算，高温下金属热力学性质随着温度的升高，理论值逐渐偏离实验值，解决这一问题的关键在于探明高温非谐效应对热力学性质影响的机制。本项目拟采用朗之万动力学非取样的热力学积分方法，充分考虑高温非谐效应的影响，精确计算过渡金属Mo和Pt的自由能，然后根据热力学基本原理获得体系的热力学性质、吉布斯自由能以及声子色散关系等信息，从而分析高温高压下非谐效应对Mo和Pt的物态方程、热力学性质以及相变影响的规律。本项目的研究有助于理解过渡金属内非谐效应产生的物理机制，也为物态方程的准确求解提供数据支撑，并为进一步理解和研究过渡金属在高温高压下的结构、物理和化学特性提供参考。

高温高压下过渡金属的物态方程和相变研究，在地球和行星物理、武器物理、航天飞行器安全防护技术等研究领域有着重要的应用背景。材料物态方程的准确求解基于其热力学性质的精确计算，高温下金属热力学性质随着温度的升高，理论值逐渐偏离实验值，解决这一问题的关键在于探明高温非谐效应对热力学性质影响的机制。本项目采用分子动力学方法，充分考虑高温非谐效应的影响，精确计算过渡金属Mo和Pt的自由能，然后根据热力学基本原理获得体系的热力学性质、吉布斯自由能以及声子色散关系等信息，从而分析高温高压下非谐效应对Mo和Pt的物态方程、热力学性质以及相变影响的规律。本项目的研究有助于理解过渡金属内非谐效应产生的物理机制，也为物态方程的准确求解提供数据支撑，并为进一步理解和研究过渡金属在高温高压下的结构、物理和化学特性提供参考。