wangvei / source_free_Bxc_VASP

source_free_Bxc_VASP

Introduction

This code repository contains the necessary patch files for the implementation of the source-free constraint on $B_{xc}$ ( $\nabla \cdot B_{xc} = 0$ ) in VASP, which we explore in this paper. Our implementation follows from the work of Sharma et al., with the key distinction that we do not include the magnetization rescaling (i.e. $s = 1$ ).

Our implementation involves the use of parallel three-dimensional Fast Fourier Transforms in order to solve the Poisson equation for the sources in the original $B_{xc}$. Therefore it is quite efficient and requires little additional computational cost compared to noncollinear VASP.

Installation

To apply the relevant code patches, simply run the following bash script in your terminal:

$ ./apply_patch.sh

The installation script will walk you through the relevant installation steps, including:

1. The choice of VASP version to which you will be applying the patch. The current implementations include:

• VASP version 6.2.1
• VASP version 5.4.4

2. The flavor of patch: "minimal" or "full":

• The minimal patch requires fewer patches to the original source-code, and simply applies the constraint directly, such that if one runs the resulting vasp_ncl, the resulting $B_{xc}$ will be free of monopoles ( $\nabla \cdot B_{xc} = 0$ ).
• The full patch provides the following VASP INCAR flags to toggle the source-free constraint, as well as the I/O of various fields relevant to the source-free correction
  • LSOURCEFREE: toggle the $\nabla \cdot B_{xc} = 0$ constraint. LSOURCEFREE=False will result in the original vasp_ncl behavior.
  • LVXC: set to True to write $v_{xc}$ and $B_{xc}$ to the XCPOT file.
  • LSOURCEPOT: set to True to write $\nabla \phi$ to the SOURCEPOT file.
  • LAXC: set to True to write $A_{xc}$ to the AXCPOT file.
  • LPMCURRENT: set to True to write $j_p$ to the JPARAMAG file. Based on error messages from VASP, the paramagnetic current can only be calculated when KPAR=1.

To keep with the conventions of VASP, most of the volumetric data files (XCPOT, SOURCEPOT, and AXCPOT) are written in the format of the noncollinear CHGCAR ( $\rho$, $m_x$, $m_y$, $m_z$ ). For the XCPOT, the first, ${\rho}$-component is the self-consistent $\nabla \cdot B_{xc}$, and the latter three indices contain the $x$, $y$, and $z$ components of $B_{xc}$.

Visualization

A Jupyter notebook has been included, visualization/Bxc_visualize.ipynb. This minimal notebook provides the user with the means to plot $B_{xc}$, and other fields output by the patch using plotly and pymatgen, as well as other Python packages.

As an example, below is a visualization of the magnetization (from CHGCAR), $m(r)$, as a vector field, as well as $B_{xc}(r)$ (from XCPOT) as streamlines (plotly's Streamtube), for the source-free ground-state of Mn₃ZnN.

How to cite

Below is a citation to our manuscript, as a bibTex entry:

@misc{mooreRealisticNoncollinearSourceFree2023,
	title = {Realistic non-collinear ground states of solids with source-free exchange correlation functional},
	url = {http://arxiv.org/},
	urldate = {2023-10-02},
	publisher = {arXiv},
	author = {Moore, Guy C. and Horton, Matthew K. and Kaplan, Aaron D. and Griffin, Sin\'ead M. and Persson, Kristin A.},
	month = oct,
	year = {2023},
	note = {arXiv [cond-mat]},
	keywords = {Condensed Matter - Materials Science},
}

License

This repository is licensed under and MIT License shown in LICENSE.