24-core parallel performance of the new 4c Dirac-Hartree-Fock algorithm with the Dirac-Coulomb operator. A series of Au clusters (Au20 to Au40) were used for this test. The computational cost for the densityintegral contraction step has been drastically reduced to the theoretical limit with the Pauli quaternion representation.
This research aims to address a growing need in the computational chemical sciences for accurate first-principles descriptions of the relativistic quantum dynamics of many-electron systems.
The goal of this project is to apply correlated, relativistic many-body quantum chemistry methods to challenging problems in chemistry where spin-dependent effects cannot be ignored. In particular, relativistic equation-of-motion coupled-cluster (EOM-CC) approaches will be applied to Fe(II)-based spin-crossover compounds and Ni(II)-based single-molecule magnets (SMMs), which have potential applications as components in novel magnetic materials and in quantum information science. For the spin-crossover complexes, ligand-field splitings and spin-transition temperatures will be derived from electron atachment (EA) EOM-CC calculations applied to the (N-1)-electron state of the Fe(II) complex (wherein the metal center has an easy-to-describe 3d5 configuration). For the SMMs, magnetic anisotropy parameters will be derived from double ionization potential (DIP) EOM-CC theory applied to the (N+2)-electron state of Ni(II) (wherein the metal center has a similarly easy-to-describe 3d10 configuration). Relativistic CC with up to (perturbative) triple excitations will also be applied to lanthanide oxide molecules, the electronic structure of which can provide insights into larger lanthanide-containing SMMs.
Broadly, this research aims to address a growing need in the computational chemical sciences for accurate first-principles descriptions of the relativistic quantum dynamics of many-electron systems. This need is driven by emerging quantum technologies that are increasingly important in material design, as scientists and engineers seek to manipulate spins toward a variety of goals, including novel magnetic materials and quantum information science (using spin-based molecular qubits, for example). Fundamental to these scientific and technological applications are the correlated many-electron dynamics of systems driven far from equilibrium, the accurate and efficient description of which represents a grand outstanding challenge in computational chemistry, especially when considering spin-dependent processes (e.g., spin-coherence, spin-entanglement, intersystem crossing, etc.)