LaAlO3电子结构及顺电特性的第一原理计算

采用基于密度泛函理论的第一原理计算方法,研究了立方相的LaAlO3(LAO)晶体的电子结构及其在外延应力作用下的相变势能面特征和波恩有效电荷值.计算结果表明,在LAO中La-d、Al-s、p及O-p轨道电子占主要作用,Al-O的轨道杂化作用相对比较大.在平面晶格应力的作用下,考量Al-O八面体畸变对相变势能面的贡献,发现其势阱曲线表现出与传统铁电材料经典的双阱曲线不同的单阱曲线,进一步的波恩有效电荷的计算表明,其原因可能是Al-O的轨道杂化作用(电荷转移)没有达到铁电畸变所需的能量,而使LAO成为顺电体.

First-principles Investigation of the Epitaxial Strain Effects on the Electronic Structure of LaAlO3

The epitaxial strain effects and Born effective charge of the cubic LaAlO3( LAO) are investigated,using the first-principle based on density functional theory. From the results of the density of states( DOS) Mulliken distributions of LAO,the La-d,Al-s,p and O-p are predominant role of orbital electrons,and Al-O orbital hybridization effect is of relatively large. Under the stress-strain in the lattice interface,the potential well curve of LAO shows single well and is different to the traditional ferroelectric double well curve. The energy change of the relative displacement of Al atomic also shows that ferroelectric distortion of LAO in the ground state is very weak or not. The analysis of the Born effective charge shows that the Al-O orbital hybridization effect( charge transfer) did not reach the energy required for the ferroelectric distortion,leaving the LAO no ferroelectricity.