Abstract: Improved methods for manipulating and detecting spin in materials are needed for advancing the state of the art in spintronics, quantum computing, and quantum information science. Modeling spin properties from first principles allows us to find materials with desirable properties such as long spin lifetimes and strong spin orbit coupling. This work develops new methods for modeling spin dynamics and transport from first principles which are highly versatile and successfully predict properties for a wide range of systems and phenomena. Using density-matrix dynamics, we can predict spin lifetimes in materials and examine non-trivial dependence from external magnetic fields. The interplay of reversible and irreversible spin relaxation processes leads to a complex dependence of spin lifetimes on the direction and magnitude of magnetic fields, relevant for spintronics and quantum information applications. In addition to spin dynamics, we also model spin transport. We introduce a computational framework for first-principles density matrix transport within the Wigner function formalism to predict transport of quantum-mechanical degrees of freedom such as spin over long time and length scales. This framework facilitates simulation of spin dynamics and transport from first principles, while accounting for electron-phonon scattering at device length scales. Overall, these frameworks are highly general, i.e. not constrained to any specific Hamiltonians, and accurately account for the electron-electron and electron-phonon interactions which dominate spin properties. Ultimately, these approaches expand the set of materials and spin-relevant phenomena that can be studied from first-principles.
