分子动力学方法模拟压强对Bi4Ti3O12铁电相变行为的影响

摘要

Pressure-induced phase transition of Bi4Ti3O12 (BIT) was studied using a shell model via molecular dynamics 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 39.4μC/cm2 in the x direction and 0 in the z direction at 300K, which were in reasonable agreement with the experimental values. The pressure-induced phase transition of BIT was also calculated. It was observed that BIT single 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.%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/cm2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-2 GPa到24 GPa范围内,经历了两次结构相变,分别发生在6 GPa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.