BaTiO3铁电体中应变-极化耦合效应的分子动力学模拟

Molecular Dynamics Simulation of the Strain-polarization Coupling in BaTiO_3 Ferroelectrics

基于一种修正的壳模型分子动力学方法研究了BaTiO_3铁电体的应变-极化耦合效应.采用DL_ POLY软件包,首先模拟了BaTiO_3铁电体的晶格常数和自发极化,取得了与实验较为一致的结果.在此基础上,对BaTiO_3的极化翻转过程和场致应变效应进行了模拟.模拟结果清楚地表明了BaTiO_2铁电体中存在着较强的应变-极化耦合效应.进一步模拟了不同应变条件下的极化强度.结果表明,在压应变条件下,体系的自发极化强度增加,且极化强度与应变量近似地成线性关系.而在拉应变条件下,体系自发极化强度迅速降低.当双轴向拉应变达到0.8%时,体系沿c轴的极化强度消失,同时在a方向出现不为零的极化强度,这表明极化强度发生了90°旋转.

Based on a modified shell model, the strain-polarization coupling was studied by molecular dynamics simulations. Using DL_POLY software packages, the lattice constant and spontaneous polarization were calculated and the results were in good agreement with experiments. The polarization switching process and the filed induced strain effects were further simulated. The results clearly suggested the existence of strong strain-polarization coupling effects in BaTiO3. Finally, the dependence of polarization on the strain was studied. Under compressive strain, the spontaneous polarization increases almost linearly with increasing strain. However, under tensile strain, the polarization decreases rapidly. When the biaxial tensile strain εs reaches 0.8%, the polarization along the c axis disappears and a non-zero polarization value exists along the a axis, indicating a 90° rotation of the polarization.