Ning Bo-Yuan, Ning Xi-Jing
Institute of Modern Physics, Fudan University, Shanghai 200433, People's Republic of China.
Applied Ion Beam Physics Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
J Phys Condens Matter. 2022 Aug 19;34(42). doi: 10.1088/1361-648X/ac8907.
For realistic crystals, the free energy strictly formulated in ensemble theory can hardly be obtained because of the difficulty in solving the high-dimension integral of the partition function, the dilemma of which makes it even a doubt if the rigorous ensemble theory is applicable to phase transitions of condensed matters. In the present work, the partition function of crystal vanadium under compression up to 320 GPa at room temperature is solved by an approach developed very recently, and the derived equation of state is in a good agreement with all the experimental measurements, especially the latest one covering the widest pressure range up to 300 GPa. Furthermore, the derived Gibbs free energy proves the very argument to understand most of the experiments reported in the past decade on the pressure-induced phase transition, and, especially, a novel phase transition sequence concerning three different phases observed very recently and the measured angles of two phases agree with our theoretical results excellently.
对于实际晶体，由于求解配分函数的高维积分存在困难，在系综理论中严格表述的自由能几乎无法得到，这种困境甚至让人怀疑严格的系综理论是否适用于凝聚态物质的相变。在本工作中，通过最近发展的一种方法求解了室温下高达320 GPa压力下晶体钒的配分函数，导出的状态方程与所有实验测量结果都非常吻合，特别是最新的一项涵盖高达300 GPa最宽压力范围的测量。此外，导出的吉布斯自由能证明了理解过去十年报道的大多数关于压力诱导相变实验的关键论据，尤其是最近观察到的涉及三个不同相的新型相变序列以及两个相的测量角度与我们的理论结果非常吻合。
