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. 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.

11 pages, 13 figures

References in corpus (7)

• Spin in Density-Functional Theory
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• U(1)$\times$SU(2) Gauge Invariance Made Simple for Density Functional Approximations
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Cited by in corpus (5)

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• A Snapshot of Time-Dependent Density-Functional Theory
• Magnetization dynamics with time-dependent spin-density functional theory: significance of exchange-correlation torques
• Exchange torque in noncollinear spin density functional theory with a semilocal exchange functional
• Spin waves in doped graphene: a time-dependent spin-density-functional approach to collective excitations in paramagnetic two-dimensional Dirac fermion gases