钛酸钡的光学性质及其体积效应

Optical properties of BaTiO_3 and its volume effects

钛酸钡(BaTiO_3, BTO)是铁电物理学和材料学领域具有代表性的研究对象.本文基于准粒子相互作用的GW方法研究BTO材料的光学性质,并研究了等应变情况下的体积效应.第一性计算结果表明,考虑了激子效应的GW (格林函数(G)-库仑势(W))方法得到的激发态性质更接近实验结果.引入等应变调控,发现体积膨胀会导致光学吸收峰红移,体积压缩则光学吸收峰蓝移.同时,探究了体积变化对BTO块材的自发极化和电子结构的影响,发现体积膨胀会使钛原子的d轨道和氧原子的p轨道杂化更显著,进一步导致材料自发极化的增大,而体积压缩对自发极化和dp杂化的影响正好相反.通过比较研究,还发现等应变的体积效应对极化的影响不如等应力体积效应明显.

BaTi03(BTO)is a typical studying object both in ferroelectrics and in material science.By the GW method,optical property of BTO is investigated,and its volume effect under the case of iso-strain is also studied.It is found that the results of excited states are closer to the experimental results with the consideration of electron-hole interaction in the framework of GW method.Considering the volume effect,we obtain that the red shift of the peaks of optical absorption occurs under the expansion of volume,and the blue shift appears when the BTO is compressed.At the same time,the polarization and the hybridization between d orbital of Ti atom and p orbital of O atom are enhanced for the case of volume expansion,however,things will be opposite under the compression of volume.Furthermore,the volume effect in the iso-strain case is less dramatic than in the iso-stress case.