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

## TL;DR

The paper introduces CoFFEE, a Python-based tool implementing FNV correction scheme to accurately compute formation energies and eigenvalues of charged defects in various material geometries, improving defect simulation accuracy.

## Contribution

It presents CoFFEE, a versatile and optimized Python code that applies FNV corrections for charged defect simulations across different material shapes.

## Key findings

- CoFFEE effectively corrects formation energies and eigenvalues.
- The code supports diverse geometries including bulk, slab, wires, and nanoribbons.
- Parallelization and optimization enhance computational efficiency.

## Abstract

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.