Timo Fleig

TL;DR: DIRAC allows for the inclusion of environmental effects through three different classes of increasingly sophisticated embedding approaches: the implicit solvation polarizable continuum model, the explicit polarizable embedding model, and the frozen density embedding models.

TL;DR: In this article, a two-component relativistic configuration interaction program is presented, based on the method of generalized active spaces which has been extended from a nonrelativistic implementation to make use of twocomponent Hamiltonians and time reversal and double point group symmetry at both the spinor and Slater determinant level.

TL;DR: DIRAC as discussed by the authors is a freely distributed general-purpose program system for one-, two-, and four-component relativistic molecular calculations at the level of Hartree-Fock, Kohn-Sham (including range-separated theory), multiconfigurational self-consistent field, multireference configuration interaction, electron propagator, and various flavors of coupled cluster theory.

TL;DR: In this article, the extension of a relativistic double group configuration interaction (CI) formalism to the use of 2-and 4-spinors is presented, and the theoretical aspects of the formalism that is needed to work with spinors that are optimized with a Hartree-Fock scheme that includes spin-orbit coupling.

TL;DR: The modular implementation of the double group configuration interaction program into a multiconfiguration self-consistent-field (MCSCF) code allows for the treatment of large CI expansions in both the spinor optimization step and the post- MCSCF dynamic electron correlation step.