随着精密制造业的发展，对超硬材料的需求日益迫切。碳在高压下的相变是制备超硬材料的关键。然而，碳势能面非常复杂，石墨在高温和室温下相变机制和相变产物完全不同，目前对其中的物理本质尚不清楚。由于缺乏温度、单轴压力对相变影响的了解，严重阻碍了新型超硬材料的设计与合成。本课题基于密度泛函方法（DFT）和势能面表面随机行走方法（SSW）来研究碳在高压下的势能面和石墨在高压下的相变微观机制。本研究将深入考察外界条件对势能面的影响，从原子级别阐述温度和应力对相变机理的作用。通过自行拟合一套完善的碳经验式，并利用经验式对石墨进行超大体系分子动力学模拟来获得高压下的原子结构，进一步模拟XRD，并与实验进行对比，从分子动力学的角度理解碳原子的运动情况。通过结合DFT和分子动力学模拟，对相变机理进行全方位的研究。总结碳的相变规律，为预测新型的超硬材料提供理论依据，进而开发合成新型的超硬材料。

With the development of precision manufacturing, the demand for superhard materials is becoming more and more urgent. The carbon under high pressure is the crucial to the synthesis of superhard materials, however, the phase transition energy landscape is extremely complex. It is well knowledge that the product and phase transition mechanism are quite different when at different temperature。still, the original of such difference is still unclear. Lacking the knowledge of temperature and uniaxial pressure on the phase transition, the design and synthesis of new superhard materials are hindered. In this research, using the density functional theory (DFT) and the potential energy surface random walk method (SSW), we systemically study the potential energy surface of carbon and the phase transition mechanism under high pressure. The effects of temperature and stress on the phase transition mechanism are explained at atomic level by investigating the effects of external conditions. By fitting a set of carbon formula, we can use large molecular dynamics to obtain graphite atomic structure under high pressure. We can compare the simulate XRD with the experimental data. With the help of DFT+SSW and molecular dynamics simulation, we can get a deep insight to the phase transition mechanism. By this project, we can provide a systemically theoretical basis for designing new superhard materials.