DIRAC Molecular Program

The molecular orbitals in the nonrelativistic and one-component calculations and the large component in the Dirac-Fock functions were spanned in the Cd s Ap9d)l[9slp6d basis of [63] and the H (5s 2p)/[35 l/>] set [61]. Contraction coefficients were taken from corresponding atomic SCF calculations. The basis for the small components in the Dirac-Fock calculations is derived by the MOLFDIR program from the large-component basis. The basis set superposition error is corrected by the counterpoise method [64]. The Breit interaction was found to have a very small effect and is therefore not included in the results. 

On the other hand, in the pioneering DHF and post-DHF program package MOLFDIR [3] and the well-developed four-component relativistic program package DIRAC [4], the molecular four-component spinors are expanded into decoupled... 

Visser, O., Aerts, P. J. C. and Visscher, L. (1991c) Open Shell Relativistic Molecular Dirac-Hartree-Fock SCF-Program. In Wilson etal. (1991), pp. 185-195. 

Edelstein, 1978, J. Inorg. Nucl. Chem. 40, 69. DeJong, W.A., L. Visscher, 0. Visser, P.J.C. Aerts and W.C. Nieuwpoort, 1994, MOLFDIR a program package for molecular Dirac-Fock-CI calculations, in New Challenges in Computational Quantum Chemistry, eds R. Broer, P.J.C. Aerts and P.S. Bagus (Department of Chemical Sciences and Material Science Centre, University of Groningen, Netherlands). 

In the molecular sciences it is most appropriate to adopt a pragmatic attitude toward the Dirac equation in order to set up a theory which closely resembles nonrelativistic many-electron theory. We will see that we can afford a number of approximations designed such that the numerical effect on physical observables still resembles that of a truly relativistic many-electron theory. Hence, we proceed from the fundamental physical principles of Einstein s special theory of relativity to approximations of different degree. As a matter of fact this is exactly the program of relativistic quantum chemistry that we shall start to develop in this chapter. 

Open Shell Relativistic Molecular Dirac-Hartree-Fock SCF-Program. In Wilson etal. [1168], p. 185-195. 

T. Saue, M. S. Thesis, Department of Chemistry, University of Oslo, 1991. Development of a Dirac-Hartree-Fock Program for Molecular Calculations. 

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