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 o relativistic effective potentials with spin–orbit operators. IV. Cs through Rn

Ross, Ronald J.; Powers, Joseph M.; Atashroo, T.; Ermler, Walter C.; LaJohn, L.A.; Christiansen, P. A.

doi:10.1063/1.458934

Cited by 593 publications

(284 citation statements)

References 15 publications

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“…3 In particular, several sets of ECPs exist for the third-series transition metal elements. Some of them are ultimately based upon the Phillips-Kleinman equation 4 and rely on the pseudo-orbital transformation that produces nodeless valence pseudo-orbitals; this is the case of the pseudopotentials produced by Bachelet et al, 5 Hay and Wadt, 6,7 Ross et al, 8 and Andrae et al 9 Some others are based on the Huzinaga-Cantu equation 10 and lead to valence orbitals with the same nodal structure as the all-electron orbitals; this is the case of the model potentials produced by Sakai et al 11 Also based on the Huzinaga-Cantu equation, the ab initio model potential ͑AIMP͒ 12 method resulted from the implementation of two ideas which contrast with the basics of all the other ECP methods: ͑i͒ the core model potentials are obtained directly from the frozen core orbitals, without resorting to parametrization procedures based on the valence orbitals, and ͑ii͒ the components of the core model potentials must mimic the operators that they substitute as much as possible, while reducing the computing time. Accordingly, nonrelativistic AIMPs ͑NR-AIMP͒ and spin-free relativistic AIMPs derived from atomic Cowan-Griffin 13 calculations ͑CG-AIMP͒ have been produced and successfully monitored for the main-group elements, 12,14,15 and for the firstseries and second-series transition metal elements, 14,16,17 but they are not available for the third-series transition metal elements.…”

Section: Introductionmentioning

confidence: 99%

The ab initio model potential method: Third-series transition metal elements

Casarrubios

Seijo

1999

The Journal of Chemical Physics

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In this paper we present nonrelativistic and relativistic core ab initio model potentials ͑AIMPs͒ and valence basis sets for La and the third-series transition metal elements. The relativistic AIMPs are derived from atomic Cowan-Griffin calculations; they are made of a spin-free part and a one-electron spin-orbit operator according to Wood and Boring. The core potentials correspond to the 62-electron core ͓Cd,4f ͔. The valence basis sets are optimized and spin-orbit corrected. We present monitoring spin-free calculations on the atoms, singly ionized ions and monohydrides of the ten elements, which show a good performance overall. A spin-free-state-shifted spin-orbit-configuration interaction calculation on Pt, which uses empirical spin-free data and which is expected to be essentially free from spin-free deficiencies, points out that the quality of the spin-orbit operators is very good.

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Section: Introductionmentioning

confidence: 99%

The ab initio model potential method: Third-series transition metal elements

Casarrubios

Seijo

1999

The Journal of Chemical Physics

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“…The relativistic effective core potential of Ross et al 59 was used, which replaces the 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, and 4d electrons of Cs. The basis set used was built on their 5s,5p,4d set ͑contracted to 4s,3p,2d͒.…”

Section: B Ab Initio Calculationsmentioning

confidence: 99%

The structure of alkali halide dimers: A critical test of ionic models and new ab initio results

Törring

Biermann

Hoeft

et al. 1996

The Journal of Chemical Physics

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The structure of alkali halide dimers: A critical test of ionic models and new ab initio results. T. Torring, S. Biermann, J. Hoeft, R. Mawhorter, R. J. Cave, and C. Szemenyei, J. Chem. Phys. 104, 8032 (1996) In semiempirical ionic models a number of adjustable parameters have to be fitted to experimental data of either monomer molecules or crystals. This leads to strong correlations between these constants and prevents a unique test and a clear physical interpretation of the fit parameters. Moreover, it is not clear whether these constants remain unchanged when the model is applied to dimers or larger clusters. It is shown that these correlations can be substantially reduced when reliable information about dimers is available from experiments or ab initio calculations. Starting with Dunham coefficients of the monomer potential determined from microwave measurements, we have calculated the monomer to dimer bond expansion and the bond angle without any additional adjustable parameter. Assuming that the overlap repulsion between nearest neighbors remains unchanged, the bond expansion is mainly determined by the simple Coulomb repulsion between equally charged ions and depends only very little on the effective ion polarizabilities. Deviation of the bond angle from 90°sensitively tests the difference of effective polarizabilities of the two ions. A comparison with previously available data and new ab initio MP2 results presented here for the heavy-atom containing dimers shows that bond angles can be modeled reasonably well with SeitzRuffa corrected Pauling polarizabilities while calculated bond expansions are much too long. This shows that changes of the overlap repulsion term must be considered for reliable predictions of the structure of dimers and larger clusters.

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“…23,24 The CRENBL ECP basis 25,26 is used for atoms larger than Kr. All (TD-)DFT geometry optimizations and subsequent frequency calculations are carried out using the Q-Chem 4.2 program package, 27 employing a EulerMaclaurin -Lebedev product quadrature grid comprising 75 radial points and 302 angular points per radial point, with an SCF convergence threshold of 10 −8 and geometry optimization thresholds decreased by an order of magnitude from their default values.…”

Section: Methodsmentioning

confidence: 99%

Quadratic Corrections to Harmonic Vibrational Frequencies Outperform Linear Models

Sibaev

Crittenden

2015

J. Phys. Chem. A

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Simulating accurate infrared spectra is a longstanding problem in computational quantum chemistry. Linearly scaling harmonic frequencies to better match experimental data is a popular way of approximating anharmonic effects while simultaneously attempting to account for deficiencies in ab initio method and/or basis set. As this approach is empirical, it is also non-variational and unbounded, so it is important to separate and quantify errors as robustly as possible. Eliminating the confounding factor of methodological incompleteness enables us to explore the intrinsic accuracy of the scaling approach alone. We find that single-coefficient linear scaling methods systematically overcorrect low frequencies, while generally undercorrecting higher frequencies. A two-parameter polynomial model gives significantly better predictions without systematic bias in any spectral region, while a single-parameter quadratic scaling model is parameterized to minimize overcorrection errors while only slightly decreasing predictive power.

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A b i n i t i o relativistic effective potentials with spin–orbit operators. IV. Cs through Rn

Cited by 593 publications

References 15 publications

The ab initio model potential method: Third-series transition metal elements

The ab initio model potential method: Third-series transition metal elements

The structure of alkali halide dimers: A critical test of ionic models and new ab initio results

Quadratic Corrections to Harmonic Vibrational Frequencies Outperform Linear Models

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