# Removing all periodic boundary conditions: Efficient non-equilibrium Green function calculations

## TL;DR

This paper introduces a computational method that calculates electronic structure and transport without relying on periodic boundary conditions, reducing artifacts and computational costs in non-equilibrium Green function simulations.

## Contribution

The authors develop and implement a new approach that eliminates the need for periodic super-cells in Green function calculations, improving accuracy and efficiency.

## Key findings

- Reduces CPU-hours compared to super-cell methods
- Successfully applied to graphene defect and junction examples
- Eliminates spurious periodic images and interference effects

## Abstract

We describe a method and its implementation for calculating electronic structure and electron transport without approximating the structure using periodic super-cells. This effectively removes spurious periodic images and interference effects. Our method is based on already established methods readily available in the non-equilibrium Green function formalism and allows for non-equilibrium transport. We present examples of a N defect in graphene, finite voltage bias transport in a point-contact to graphene, and a graphene-nanoribbon junction. This method is less costly, in terms of CPU-hours, than the super-cell approximation.