# libvdwxc: A library for exchange-correlation functionals in the vdW-DF family

## TL;DR

libvdwxc is a scalable, efficient library for evaluating vdW-DF exchange-correlation functionals, enabling large-scale extit{ab initio} calculations in DFT codes with high parallel performance.

## Contribution

The paper introduces libvdwxc, a versatile library that improves the efficiency and scalability of vdW-DF functional evaluations in DFT calculations.

## Key findings

- Benchmarking shows high numerical accuracy on the S22 test set.
- Parallel performance scales well up to 9696 atoms.
- Enables extit{ab initio} calculations of nanometer-scale complexes.

## Abstract

We present libvdwxc, a general library for evaluating the energy and potential for the family of vdW-DF exchange--correlation functionals. libvdwxc provides an efficient implementation of the vdW-DF method and can be interfaced with various general-purpose DFT codes. Currently, the GPAW and Octopus codes implement interfaces to libvdwxc. The present implementation emphasizes scalability and parallel performance, and thereby enables \textit{ab initio} calculations of nanometer-scale complexes. The numerical accuracy is benchmarked on the S22 test set whereas parallel performance is benchmarked on ligand-protected gold nanoparticles ($\text{Au}_{144}(\text{SC}_{11}\text{NH}_{25})_{60}$) up to 9696 atoms.