Spin-Dependent NGWFs in ONETEP: Better Basis, Better Magnetism
Dr. Miguel Escobar Azor, Department of Chemistry, University of Warwick
Spin-polarized materials play an important role in areas ranging from magnetic nanostructures to two-dimensional van der Waals magnets. Accurate first-principles simulations of such systems remain challenging within linear-scaling density functional theory (LS-DFT), where the two spin channels are typically constrained to share a common variational basis, a limitation that can reduce accuracy for systems with strong spin polarization or magnetic order.
This talk presents a spin-dependent extension of the non-orthogonal generalized Wannier function (NGWF) formalism within the ONETEP LS-DFT code, in which each spin channel is described by its own independently optimized set of localized orbitals. This provides a more flexible and physically faithful representation of the spin-polarized electronic density, without significantly increasing computational cost.
The method is applied to a diverse set of systems: localized magnetic defects in hexagonal boron nitride, Fe(III) transition-metal complexes, bilayer CrI3, and both bulk and nanocluster ferromagnetic cobalt. In each case, spin-dependent NGWFs yield lower total energies, improved localization of spin density, and correct predictions of magnetic ground states, including cases where the shared-basis approach fails entirely. These improvements are particularly pronounced when combined with DFT+U and DFT+U+J Hubbard corrections.