Enabling Electronic Structure Calculations of High Z Element Containing Materials Using Dirac Relativistic DFT Methods

Abstract

Novel properties may be induced in a host material by doping it with high Z elements to alter its underlying electronic states. Presently, no method exists that can accurately capture both large system sizes and the intricate fundamental physics of the induced multiplet states in the electronic structure. As part of a collaborative effort to merge a configuration interaction (CI) and density functional theory (DFT) method into one method that is capable of calculating the properties of high Z doped materials, an entirely new scheme for relativistic consideration of a localized orbital basis set and energy calculation was devised. This work presents a novel scheme for the creation of single-component scalar relativistic and four-component fully relativistic atomic orbital basis sets of Gaussian-type functions. A minimal norm least squares method was used to fit numerically represented, four-component Dirac spinors into a set of Gaussian basis functions possessing exponential coefficients expressed over a geometric series. A simultaneous parameter sweep of both the maximum range of exponential coefficients and number of terms in the expansion for each quantum number was used to optimize the basis set efficiency. An algorithm that circumvents the error prone direct calculation of relativistic kinetic energy terms has been adapted from the CI method of our collaborator into one compatible with the Orthogonalized Linear Combination of Atomic Orbitals DFT package. Lastly, an application of the current state-of-the-art in high-throughput relativistic DFT to a well-known material science problem will be discussed.