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## Exchange-correlation magnetic fields in spin-density-functional theory

## Abstract

In spin-density-functional theory for noncollinear magnetic materials, the Kohn-Sham system features exchange-correlation (xc) scalar potentials and magnetic fields. The significance of the xc magnetic fields is not very well explored; in particular, they can give rise to local torques on the magnetization, which are absent in standard local and semilocal approximations. We obtain exact benchmark solutions for two electrons on four-site extended Hubbard lattices over a wide range of interaction strengths, and compare exact xc potentials and magnetic fields with approximations obtained from orbital-dependent xc functionals. Here, the xc magnetic fields turn out to play an increasingly important role as systems becomes more and more correlated and the electrons begin to localize; the effects of the xc torques, however, remain relatively minor. The approximate xc functionals perform overall quite well, but tend to favor symmetry-broken solutions for strong interactions.

- Authors:

- Univ. of Missouri, Columbia, MO (United States)

- Publication Date:

- Research Org.:
- Univ. of Missouri, Columbia, MO (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division

- OSTI Identifier:
- 1561956

- Grant/Contract Number:
- SC0019109

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Physical Review B

- Additional Journal Information:
- Journal Volume: 100; Journal Issue: 12; Journal ID: ISSN 2469-9950

- Publisher:
- American Physical Society (APS)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; density-functional theory; noncollinear magnetism; Hubbard model

### Citation Formats

```
Pluhar, III, Edward A., and Ullrich, Carsten A. Exchange-correlation magnetic fields in spin-density-functional theory. United States: N. p., 2019.
Web. doi:10.1103/PhysRevB.100.125135.
```

```
Pluhar, III, Edward A., & Ullrich, Carsten A. Exchange-correlation magnetic fields in spin-density-functional theory. United States. doi:10.1103/PhysRevB.100.125135.
```

```
Pluhar, III, Edward A., and Ullrich, Carsten A. Mon .
"Exchange-correlation magnetic fields in spin-density-functional theory". United States. doi:10.1103/PhysRevB.100.125135.
```

```
@article{osti_1561956,
```

title = {Exchange-correlation magnetic fields in spin-density-functional theory},

author = {Pluhar, III, Edward A. and Ullrich, Carsten A.},

abstractNote = {In spin-density-functional theory for noncollinear magnetic materials, the Kohn-Sham system features exchange-correlation (xc) scalar potentials and magnetic fields. The significance of the xc magnetic fields is not very well explored; in particular, they can give rise to local torques on the magnetization, which are absent in standard local and semilocal approximations. We obtain exact benchmark solutions for two electrons on four-site extended Hubbard lattices over a wide range of interaction strengths, and compare exact xc potentials and magnetic fields with approximations obtained from orbital-dependent xc functionals. Here, the xc magnetic fields turn out to play an increasingly important role as systems becomes more and more correlated and the electrons begin to localize; the effects of the xc torques, however, remain relatively minor. The approximate xc functionals perform overall quite well, but tend to favor symmetry-broken solutions for strong interactions.},

doi = {10.1103/PhysRevB.100.125135},

journal = {Physical Review B},

number = 12,

volume = 100,

place = {United States},

year = {2019},

month = {9}

}

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