论文标题
使用广义的Wannier函数在恒定极化下对铁电的第一原理计算
First-principles calculations for ferroelectrics at constant polarization using generalized Wannier functions
论文作者
论文摘要
本地化的Wannier功能提供了一个有效，直观的框架，以计算第一原理的电化极化。它们还可以用于表示固定电场上的电子系统并确定绝缘材料的介电特性。在这里，我们开发了一种基于Wannier功能的形式主义，以在固定的极化下执行第一原理计算。这种方法允许提取晶体的极化 - 能源景观，从而支持极性材料的理论研究。为了促进计算，我们实施了一种准牛顿方法，该方法同时放松了内部坐标并调节固定极化时晶体中的电场。该方法用于研究$ \ mathrm {batio_3} $和$ \ mathrm {pbtio_3} $的铁电行为。由于Wannier功能提供的局部轨道图片，对驱动两种化合物的铁电的物理过程进行了检查。因此，可以准确可视化铁电扭曲下化学键的变化。突出显示了$ \ mathrm {batio_3} $和$ \ mathrm {pbtio_3} $的铁电特性的差异。它可以追溯到其电子结构的特殊性。
Localized Wannier functions provide an efficient and intuitive framework to compute electric polarization from first-principles. They can also be used to represent the electronic systems at fixed electric field and to determine dielectric properties of insulating materials. Here we develop a Wannier-function-based formalism to perform first-principles calculations at fixed polarization. Such an approach allows to extract the polarization-energy landscape of a crystal and thus supports the theoretical investigation of polar materials. To facilitate the calculations, we implement a quasi-Newton method that simultaneously relaxes the internal coordinates and adjusts the electric field in crystals at fixed polarization. The method is applied to study the ferroelectric behavior of $\mathrm{BaTiO_3}$ and $\mathrm{PbTiO_3}$ in tetragonal phases. The physical processes driving the ferroelectricity of both compounds are examined thanks to the localized orbital picture offered by Wannier functions. Hence, changes in chemical bonding under ferroelectric distortion can be accurately visualized. The difference in the ferroelectric properties of $\mathrm{BaTiO_3}$ and $\mathrm{PbTiO_3}$ is highlighted. It can be traced back to the peculiarities of their electronic structures.
