Relativistic quantum chemistry: the MOLFDIR program package

Visscher, Lucas; Visser, O.; Aerts, P. J. C.; Merenga, H.; Nieuwpoort, W.C.

doi:10.1016/0010-4655(94)90115-5

Cited by 325 publications

(197 citation statements)

References 44 publications

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“…The neglect of the Gaunt interaction is important as is apparent by looking at the fourth and fifth column of Table III where we list the Dirac-Coulomb and Dirac-Coulomb-Gaunt results computed with the MOLFDIR program. 26,27 The effect of the Gaunt interaction is an almost constant shift of 20 cm Ϫ1 that reduces the computed splitting. The spin-other-orbit contribution to the splitting increases slightly with the correlation treatment, and we give an estimated ͑final͒ value for the SD9 CI calculation including the estimated Gaunt contribution at this level of correlation from the MOLFDIR CC calculations.…”

Section: B a Molecular Example: Clomentioning

confidence: 99%

The generalized active space concept for the relativistic treatment of electron correlation. II. Large-scale configuration interaction implementation based on relativistic 2- and 4-spinors and its application

Fleig

Olsen

Visscher

2003

The Journal of Chemical Physics

151

113

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The extension of a relativistic double group configuration interaction ͑CI͒ formalism to the use of 2-and 4-spinors is presented. We first elucidate the theoretical aspects of the formalism that is needed to work with spinors that are optimized with a Hartree-Fock scheme that includes spinorbit coupling. We then describe a new general implementation for the computation of sigma vectors and n-particle density matrices that occur in direct CI algorithms. Sample calculations of the spin-orbit splitting in atoms with one particle or hole in an otherwise closed shell configuration ᐉ 1 (ᐉϭ1,2,3) and molecules containing such atoms illustrate the advantage of treating this effect in a basis of true spinors rather than in a basis of scalar relativistic orbitals as is conventionally done.

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Section: B a Molecular Example: Clomentioning

confidence: 99%

The generalized active space concept for the relativistic treatment of electron correlation. II. Large-scale configuration interaction implementation based on relativistic 2- and 4-spinors and its application

Fleig

Olsen

Visscher

2003

The Journal of Chemical Physics

151

113

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“…The MOLFDIR program suite 38 needed only slight modifications to extend its two-component ͑nonrelativistic͒ option to the desired quasirelativistic one in which both scalar and spin-orbit relativistic effects can be treated. The changed part of the MOLFDIR was the RELONEL ͑Ref.…”

Section: Methods and Computational Detailsmentioning

confidence: 99%

“…39 The spin-orbit atomic integrals were obtained from the AMFI code from one of us ͑B.S.͒. 40 Both types of integrals were transformed into MOLFDIR double-group irreducible representations 31,33,38 by an interface program that exploits the fact that MOLFDIR atomic basis functions are cubic combinations of Cartesian functions. An independent two-component SCF program in the C 1 symmetry based only on MOLCAS and AMFI integrals was further written to check the MOLFDIR DK͑ϩMFSO͒ SCF energy values.…”

Section: Methods and Computational Detailsmentioning

confidence: 99%

Inclusion of mean-field spin–orbit effects based on all-electron two-component spinors: Pilot calculations on atomic and molecular properties

Iliaš

Kellö

Visscher

et al. 2001

The Journal of Chemical Physics

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An implementation of a two-component all-electron ( j j/ ) treatment of both scalar and spinorbit relativistic effects in the MOLFDIR program suite is presented. Relativity is accounted for by Douglas-Kroll transformed one-electron operators: scalar ͑spin-free͒ and so called mean-field spinorbit terms. The interelectronic interaction is represented by the nonrelativistic Coulomb operator. High-level correlated calculations of properties of several systems ͑FO, ClO, Cl, O 2 ϩ , O 2 Ϫ , Tl, and TlH͒ where spin-orbit effects play a dominant role are presented and compared with other data. Agreement with Dirac-Coulomb͑-Gaunt͒ reference values is in general very good.

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“…14 Furthermore, the two-component Kramers restricted coupled-cluster (KRCC) 15 calculation was made feasible by interfacing ARGOS into the all-electron four-component MOLFDIR suite of programs, 18 which was then further modified and combined with a spinor rotation code to allow Kramers restricted competeactive-space SCF (KRCASSCF) calculation. 16 Lee 19 provided an extensive review on our former implementations and test results of a number of two-component methods, showing that it is possible to obtain reasonable spectroscopic and thermodynamic data for molecules containing heavy elements by using SOREP.…”

Section: Introductionmentioning

confidence: 99%

KPACK: Relativistic Two-component Ab Initio Electronic Structure Program Package

Kim¹,

Lee²

2013

Bulletin of the Korean Chemical Society

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We describe newly developed software named KPACK for relativistic electronic structure computation of molecules containing heavy elements that enables the two-component ab initio calculations in Kramers restricted and unrestricted formalisms in the framework of the relativistic effective core potential (RECP). The spin-orbit coupling as relativistic effect enters into the calculation at the Hartree-Fock (HF) stage and hence, is treated in a variational manner to generate two-component molecular spinors as one-electron wavefunctions for use in the correlated methods. As correlated methods, KPACK currently provides the two-component second-order Møller-Plesset perturbation theory (MP2), configuration interaction (CI) and complete-activespace self-consistent field (CASSCF) methods. Test calculations were performed for the ground states of group-14 elements, for which the spin-orbit coupling greatly influences the determination of term symbols. A categorization of three procedures is suggested for the two-component methods on the basis of spin-orbit coupling manifested in the HF level.

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Relativistic quantum chemistry: the MOLFDIR program package

Cited by 325 publications

References 44 publications

The generalized active space concept for the relativistic treatment of electron correlation. II. Large-scale configuration interaction implementation based on relativistic 2- and 4-spinors and its application

The generalized active space concept for the relativistic treatment of electron correlation. II. Large-scale configuration interaction implementation based on relativistic 2- and 4-spinors and its application

Inclusion of mean-field spin–orbit effects based on all-electron two-component spinors: Pilot calculations on atomic and molecular properties

KPACK: Relativistic Two-component Ab Initio Electronic Structure Program Package

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