Relativistic all-electron molecular Hartree-Fock-Dirac-(Breit) calculations on CH4, SiH4, GeH4, SnH4, PbH4

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

doi:10.1007/bf01134864

Cited by 82 publications

(36 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This corresponds to the zerothorder term of an expansion of the full relativistic two-electron interaction in orders of c −2 , which is sufficient for most chemical purposes. 33 Although the two-electron operator in the Dirac-Coulomb…”

Section: Theorymentioning

confidence: 99%

Theoretical ⁵⁷Fe Mössbauer spectroscopy: isomer shifts of [Fe]-hydrogenase intermediates

Hedegård

Knecht

Ryde

et al. 2014

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Mössbauer spectroscopy is an indispensable technique and analytical tool in iron coordination chemistry. The linear correlation between the electron density at the nucleus ("contact density") and experimental isomer shifts has been used to link calculated contact densities to experimental isomer shifts. Here we have investigated for the first time relativistic methods of systematically increasing sophistication, including the eXact 2-Component (X2C) Hamiltonian and a finite-nucleus model, for the calculation of isomer shifts for iron compounds.While being of similar accuracy as the full four-component treatment, X2C calculations are far more efficient. We find that effects from spin orbit coupling can safely be neglected, leading to further speed up. Linear correlation plots using effective densities rather than contact densities versus experimental isomer shift leads to a correlation constant a = −0.32 a −3 0 mm s −1 (PBE functional) which is in close agreement to experimental findings. Isomer shifts of similar quality can thus be obtained both with and without fitting, which is not the case if one pursues a priori a non-relativistic model approach. As an application for a biologically relevant system, we have studied three recently proposed [Fe]-hydrogenase intermediates. The structures for these intermediates were extracted from QM/MM calculations using large QM regions surrounded by the full enzyme and a solvation shell of water molecules. We show that a comparison between calculated and experimentally observed isomer shifts can be used to discriminate between the different intermediates, whereas calculated atomic charges do not necessarily correlate with Mössbauer isomer shifts. Detailed analysis shows that the difference in isomer shifts between two intermediates is due to an overlap effect.

show abstract

Section: Theorymentioning

confidence: 99%

Theoretical ⁵⁷Fe Mössbauer spectroscopy: isomer shifts of [Fe]-hydrogenase intermediates

Hedegård

Knecht

Ryde

et al. 2014

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…Due to the persistent discrepancies over the ⌬H f value of silicon gas, 34,[78][79][80][81][82] seven molecules from the G2-1 test set containing silicon atoms have been removed from our initial test set. Work is currently being carried out upon small silicon-containing compounds in order to assess and improve the errors of the ccCA-CBS methods, and more quantitatively address controversy in the gas phase enthalpy of formation of silicon.…”

Section: A Performance Of Cccamentioning

confidence: 99%

The correlation consistent composite approach (ccCA): An alternative to the Gaussian-n methods

DeYonker

Cundari

Wilson

2006

The Journal of Chemical Physics

307

327

View full text Add to dashboard Cite

An alternative to the Gaussian-n ͑G1, G2, and G3͒ composite methods of computing molecular energies is proposed and is named the "correlation consistent composite approach" ͑ccCA, ccCA-CBS-1, ccCA-CBS-2͒. This approach uses the correlation consistent polarized valence ͑cc-pV XZ͒ basis sets. The G2-1 test set of 48 enthalpies of formation ͑⌬H f ͒, 38 adiabatic ionization potentials ͑IPs͒, 25 adiabatic electron affinities ͑EAs͒, and 8 adiabatic proton affinities ͑PAs͒ are computed using this approach, as well as the ⌬H f values of 30 more systems. Equilibrium molecular geometries and vibrational frequencies are obtained using B3LYP density functional theory. When applying the ccCA-CBS method with the cc-pVXZ series of basis sets augmented with diffuse functions, mean absolute deviations within the G2-1 test set compared to experiment are 1.33 kcal mol −1 for ⌬H f , 0.81 kcal mol −1 for IPs, 1.02 kcal mol −1 for EAs, and 1.51 kcal mol −1 for PAs, without including the "high-level correction" ͑HLC͒ contained in the original Gn methods. Whereas the HLC originated in the Gaussian-1 method as an isogyric correction, it evolved into a fitted parameter that minimized the error of the composite methods, eliminating its physical meaning. Recomputing the G1 and G3 enthalpies of formation without the HLC reveals a systematic trend where most ⌬H f values are significantly higher than experimental values. By extrapolating electronic energies to the complete basis set ͑CBS͒ limit and adding G3-like corrections for the core-valence and infinite-order electron correlation effects, ccCA-CBS-2 often underestimates the experimental ⌬H f , especially for larger systems. This is desired as inclusion of relativistic and atomic spin-orbit effects subsequently improves theoretical ⌬H f values to give a 0.81 kcal mol −1 mean absolute deviation with ccCA-CBS-2. The ccCA-CBS method is a viable "black box" method that can be used on systems with at least 10-15 heavy atoms.

show abstract

“…5,[7][8][9][10] But a naive calculation of molecular properties within the DKH framework using the nonrelativistic expression for the property operator is plagued by an artifact called picture-change effect. [11][12][13][14][15][16] Recent second-order picture-change-affected DKH studies on tin compounds, for instance, revealed that following the estimates of Kellö and Sadlej 12 for the iodine nucleus in HI, one has to expect an overshoot of about 9% when calculating the electric field gradient from nonrelativistic property integrals. 17 Pioneering attempts to cope with that problem gave birth to the development of numerical finite difference schemes.…”

Section: Introductionmentioning

confidence: 99%

Analytic high-order Douglas-Kroll-Hess electric field gradients

Mastalerz

Barone²,

Lindh

et al. 2007

The Journal of Chemical Physics

View full text Add to dashboard Cite

In this work we present a comprehensive study of analytical electric field gradients in hydrogen halides calculated within the high-order Douglas-Kroll-Hess ͑DKH͒ scalar-relativistic approach taking picture-change effects analytically into account. We demonstrate the technical feasibility and reliability of a high-order DKH unitary transformation for the property integrals. The convergence behavior of the DKH property expansion is discussed close to the basis set limit and conditions ensuring picture-change-corrected results are determined. Numerical results are presented, which show that the DKH property expansion converges rapidly toward the reference values provided by four-component methods. This shows that in closed-shell cases, the scalar-relativistic DKH͑2,2͒ approach which is of second order in the external potential for both orbitals and property operator yields a remarkable accuracy. As a parameter-dependence-free high-order DKH model, we recommend DKH͑4,3͒. Moreover, the effect of a finite-nucleus model, different parametrization schemes for the unitary matrices, and the reliability of standard basis sets are investigated.

show abstract

Relativistic all-electron molecular Hartree-Fock-Dirac-(Breit) calculations on CH4, SiH4, GeH4, SnH4, PbH4

Cited by 82 publications

References 22 publications

Theoretical ⁵⁷Fe Mössbauer spectroscopy: isomer shifts of [Fe]-hydrogenase intermediates

Theoretical ⁵⁷Fe Mössbauer spectroscopy: isomer shifts of [Fe]-hydrogenase intermediates

The correlation consistent composite approach (ccCA): An alternative to the Gaussian-n methods

Analytic high-order Douglas-Kroll-Hess electric field gradients

Contact Info

Product

Resources

About

Relativistic all-electron molecular Hartree-Fock-Dirac-(Breit) calculations on CH4, SiH4, GeH4, SnH4, PbH4

Cited by 82 publications

References 22 publications

Theoretical 57Fe Mössbauer spectroscopy: isomer shifts of [Fe]-hydrogenase intermediates

Theoretical 57Fe Mössbauer spectroscopy: isomer shifts of [Fe]-hydrogenase intermediates

The correlation consistent composite approach (ccCA): An alternative to the Gaussian-n methods

Analytic high-order Douglas-Kroll-Hess electric field gradients

Contact Info

Product

Resources

About

Theoretical ⁵⁷Fe Mössbauer spectroscopy: isomer shifts of [Fe]-hydrogenase intermediates

Theoretical ⁵⁷Fe Mössbauer spectroscopy: isomer shifts of [Fe]-hydrogenase intermediates