Self-consistent potential correction for charged periodic systems

一维系统中带电缺陷的超原胞修正方案

A Finite-Size Supercell Correction Scheme for Charged Defects in One-Dimensional Systems

我们提出了一个新的有限尺寸修正方案，在密度泛函理论中计算一维系统中带电缺陷和杂质的形成能。超原胞几何结构中的能量修正是通过求解由各向异性介电常数张量描述的连续介质模型中的泊松方程来获得的，其中缺陷电荷分布来自第一性原理计算。我们实施我们的计划来研究硅纳米线中的杂质和悬挂键，并证明了带电缺陷的形成能量随着超晶胞尺寸迅速收敛。

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.…

Charged surfaces and slabs in periodic boundary conditions

Plane wave density functional theory codes generally assume periodicity in all three dimensions. This causes difficulties when studying charged systems, for instance energies per unit cell become infinite, and, even after being renormalised by the introduction of a uniform neutralising background, are very slow to converge with cell size. The periodicity introduces spurious electric fields which decay slowly with cell size and which also slow the convergence of other properties relating to the ground state charge density. This paper presents a simple self-consistent technique for producing rap…

Stability of charged sulfur vacancies in 2D and bulk MoS$_2$ from plane-wave density functional theory with electrostatic corrections

Two-dimensional (2D) semiconducting transition metal dichalcogenides such as MoS$_2$ have attracted extensive research interests for potential applications in optoelectronics, spintronics, photovoltaics, and catalysis. To harness the potential of these materials for electronic devices requires a better understanding of how defects control the carrier concentration, character, and mobility. Utilizing a correction scheme developed by Freysoldt and Neugebauer to ensure the appropriate electrostatic boundary conditions for charged defects in 2D materials, we perform density functional theory calcu…

Image charge interaction correction in charged-defect calculation

Charged-defect calculation using a periodic supercell is a significant class of problems in solid state physics. However, the finite supercell size induces an undesirable long-range image charge Coulomb interaction. Although a variety of methods have been proposed to eliminate such image Coulomb interaction, most of the previous schemes are based on a rough approximation of the defect charge screening. In this work, we present a rigorous derivation of the image charge interaction with a new defect screening model where the use of bulk macroscopic dielectric constant can be avoided. We have ver…

Pseudopotential contributions to the quadrupole moment in charged periodic systems

There has been much interest over many years in studying charged systems after the artificial imposition of periodic boundary conditions, and correcting for the resulting divergence of the electrostatic energy density. A correction for cubic cells was derived by Makov and Payne in 1995, and its leading error term is of the form $L^{-5}$ for a cube of side $L$. Most modern Density Functional Theory codes use a different treatment of the `Z$α$' energy term to that used by Makov and Payne, resulting in an error term of the form $L^{-3}$ if their correction is used unmodified. This paper shows how…