CoFFEE: Corrections For Formation Energy and Eigenvalues for charged defect simulations

Charged point defects in materials are widely studied using Density Functional Theory (DFT) packages with periodic boundary conditions. The formation energy and defect level computed from these simulations need to be corrected to remove the contributions from the spurious long-range interaction between the defect and its periodic images. To this effect, the CoFFEE code implements the Freysoldt-Neugebauer-Van de Walle (FNV) correction scheme. The corrections can be applied to charged defects in a complete range of material shapes and size: bulk, slab (or two-dimensional), wires and nanoribbons. The code is written in Python and features MPI parallelization and optimizations using the Cython package for slow steps.

材料中的带电点缺陷常借助带周期性边界条件的密度泛函理论（Density Functional Theory, DFT）软件包开展研究。通过此类模拟计算得到的形成能与缺陷能级，需要进行修正以消除缺陷与其周期性镜像之间的虚假长程相互作用贡献。为此，CoFFEE代码实现了Freysoldt-Neugebauer-Van de Walle（FNV）修正方案。该修正方案可适用于全范围形貌与尺寸的带电缺陷：块体、薄片（或二维）结构、线材与纳米带。该代码采用Python编写，并支持MPI并行计算，同时针对计算耗时步骤借助Cython工具包进行优化。