中文摘要：

在壳模型的基础上，通过分子动力学方法模拟了压强对Bi4Ti3O12（BIT）铁电相变行为的影响．为了提高模拟的准确性，在原有势参数的基础上增加了Ti-Ti短程相互作用势．计算得出了温度为300K时BIT单晶的铁电正交B2cb相在X方向和Z方向的自发极化强度分别为39．4μC／cm^2和0，与实验结果较好的吻合．然后模拟了压强对BIT相变行为的影响．模拟结果表明：BIT单晶在压强从-2GPa到24GPa范围内，经历了两次结构相变，分别发生在6GPa和20GPa处．这种对称性的改变类似于在环境压力条件下温度导致BIT单晶对称性的改变．因而模拟结果为研究压强引起BIT的相变行为提供了理论依据．

英文摘要：

Pressure-induced phase transition of Bi4Ti3O12 （BIT） was studied using a shell model via molecular dy- namics method. The Ti-Ti short range interaction potential was added to increase the accuracy of the simulation. The calculated spontaneous polarizations of ferroelectric orthorhombic B2cb phase BIT single crystal were 39.41xC/cm2 in the x direction and 0 in the z direction at 300K, which were in reasonable agreement with the ex- perimental values. The pressure-induced phase transition of BIT was also calculated. It was observed that BIT sin- gle crystal underwent two structural transformations at around 6GPa and 20GPa with increasing pressure from -2GPa to 24GPa. The accompanying symmetry changes may be the same as those observed at ambient pressure at elevated temperature. Thus the results provide a theoretical prediction of the pressure-induced phase transition in BIT.