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

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 BaTiO_3.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 straine_S 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.