分子动力学方法模拟压强对Bi4Ti3O12铁电相变行为的影响

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20 GPa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.

Study on Pressure-induced Ferroelectric Phase Transition in Bi_4Ti_3O_(12) by Molecular Dynamics Simulation

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.