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中文摘要：
本文利用第一性原理方法研究了金红石相和单斜相VO2晶体的电子结构和热力学性质.在计算中采用局域密度近似结合Hubbard U模型（LDA＋U）描述电子的局域强关联效应,同时也利用微扰密度泛函方法计算了两种相结构的声子谱.计算结果表明V原子3d电子轨道中x2-y2轨道能级分裂决定了VO2晶体在不同相结构下的金属和绝缘体特性.零温状态方程计算揭示了在68GPa时可以发生从单斜结构到金红石结构的压致相变,而V原子3d和3s轨道电子与O原子2p轨道电子的强关联效应是导致VO2晶体发生压致相变的主要原因.同时,通过对系统的吉布斯自由能计算得到了与实验结果较好符合的热致相变温度（375K）.
英文摘要：
The first principle methods have been used to investigate the electronic structure and thermal property of VO2 in rutile or monoclinic phase. The strong electronic correlation of V （3d） was described by the local density plus Hubbard U approximation,and the phonon density of states of the two phases were calculated by using perturbation density function theory. Our calculated results showed that the energy level of x2-y2 orbital of V （3d） exhibits an separation in the electronic density of stats when VO2 transfer from metallic states to insulator state. The calculated equation of states of VO2 at zero temperature discovered a pressure-induced M—I phase transition at 68 GPa. The pressure-induced M—I phase transition can be due to the strong correlation between V（3d,3s） and O（2p） orbital. Furthermore,based on the Gibbs free energy,we found that the temperature-induced phase transition is at 375 K. This is in agreement with the experimental result.
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