Noncollinear Spin Density Functional Theory (SDFT) holds the promise for describing electrons whose spins are not constrained along a common arbitrary direction. Electron distributions involving noncollinear spins can be the consequence of relativistic effects such as spin-orbit interactions or they may be required to explain the properties of magnetic materials, including phenomena like spin-dynamics.<br/><br/>We discuss the formal development and implementation of a two-component General Kohn-Sham (2c-GKS) ground state method. Our ansatz describes noncollinear spins preserving a full spatial and spin rotational invariance, it has the expected collinear limit and it is free of numerical instabilities in regions of small magnetization density. All functionals already developed for collinear GKS can be used in 2c-GKS calculations (GGAs, meta-GGAs, global and range-separated hybrid functionals). Moreover, beyond the local density approximation, a non-vanishing exchange-correlation (XC) local magnetic torque is present, while the Zero Torque Theorem (ZTT) remains satisfied globally.<br/><br/>We also present a proper linear response (LR) approach starting from a 2c-GKS ground state. The linear response XC kernel involves the same functional used to produce the unperturbed ground state density, and both the Hermitian and anti-Hermitian components of the transition density in the atomic orbital basis are involved in the response kernel. The LR-2c-GKS approach is then applied to implement a stability test for the 2c-GKS ground state, and a single-particle excited states method via a Time-Dependent (TD) 2c-GKS approach.

Noncollinear spins in density functional theory: Ground state formulation, linear response, stability and single particle excited states

255th National Meeting (2018)

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