The DIRAC code for relativistic molecular calculations

DIRAC 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. At the self-consistent-field level, a highly original scheme, based on quaternion algebra, is implemented for the treatment of both spatial and time reversal symmetry. DIRAC features a very general module for the calculation of molecular properties that to a large extent may be defined by the user and further analyzed through a powerful visualization module. It 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 model.Fil: Saue, Trond. Université Paul Sabatier; Francia. Centre National de la Recherche Scientifique; FranciaFil: Bast, Radovan. Uit The Arctic University Of Norway; NoruegaFil: Gomes, André Severo Pereira. University Of Lille.; Francia. Centre National de la Recherche Scientifique; FranciaFil: Jensen, Hans Jorgen Aa.. University of Southern Denmark; DinamarcaFil: Visscher, Lucas. Vrije Universiteit Amsterdam; Países BajosFil: Aucar, Ignacio Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Modelado e Innovación Tecnológica. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Modelado e Innovación Tecnológica; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura. Departamento de Física; ArgentinaFil: Di Remigio, Roberto. Uit The Arctic University of Norway; NoruegaFil: Dyall, Kenneth G.. Dirac Solutions; Estados UnidosFil: Eliav, Ephraim. Universitat Tel Aviv.; IsraelFil: Fasshauer, Elke. Aarhus University. Department of Bioscience; DinamarcaFil: Fleig, Timo. Université Paul Sabatier; Francia. Centre National de la Recherche Scientifique; FranciaFil: Halbert, Loïc. Centre National de la Recherche Scientifique; Francia. University Of Lille.; FranciaFil: Hedegård, Erik Donovan. Lund University; SueciaFil: Helmich-Paris, Benjamin. Max-planck-institut Für Kohlenforschung; AlemaniaFil: Ilias, Miroslav. Matej Bel University; EslovaquiaFil: Jacob, Christoph R.. Technische Universität Braunschweig; AlemaniaFil: Knecht, Stefan. Eth Zürich, Laboratorium Für Physikalische Chemie; SuizaFil: Laerdahl, Jon K.. Oslo University Hospital; NoruegaFil: Vidal, Marta L.. Department Of Chemistry; DinamarcaFil: Nayak, Malaya K.. Bhabha Atomic Research Centre; IndiaFil: Olejniczak, Malgorzata. University Of Warsaw; PoloniaFil: Olsen, Jógvan Magnus Haugaard. Uit The Arctic University Of Norway; NoruegaFil: Pernpointner, Markus. Kybeidos Gmbh; AlemaniaFil: Senjean, Bruno. Universiteit Leiden; Países BajosFil: Shee, Avijit. Department Of Chemistry; Estados UnidosFil: Sunaga, Ayaki. Tokyo Metropolitan University; JapónFil: van Stralen, Joost N. P.. Vrije Universiteit Amsterdam; Países Bajo

Quadratic response functions for a multiconfigurational self-consistent field wave-function

We describe an efficient implementation of the quadratic response function for a multiconfiguration self-consistent field reference wave function. The quadratic response function determines the hyperpolarizability and its residues determine the two-photon transition matrix elements and the transition matrix elements between excited states. We report sample calculations for the hyperpolarizability of Ne and for the two-photon transition matrix elements of Ne and H-2