Non-empirical pseudopotentials for molecular calculations

Barthelat, Jean‐Claude; Durand, Ph.; Serafini, A.

doi:10.1080/00268977700103141

Cited by 335 publications

(85 citation statements)

References 9 publications

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“…20 We use the Troullier-Martins scheme 22 to generate smooth pseudopotentials, and remove the unphysical extremely nonlocal behaviour which results from the exact exchange in a controlled manner. 17 The resulting (tabulated) pseudopotentials are then represented in a convenient analytic form suitable for use in standard quantum chemistry codes, using a fitting procedure based on the method first described by Barthelat et al 29 The version of this scheme employed here increases the efficiency and accuracy of the fitting procedure, and preserves the smoothness of the TroullierMartins pseudopotentials.…”

Section: Discussionmentioning

confidence: 99%

“…We vary the available a ql of the parameterized pseudopotential to search for a minimum of Σ where the overlap φ p l |φ p l is maximized and the error in the eigenvalue |ǫ p l − ǫ p l | is minimized separately for each available l. In the original formulation of Barthelat et al 29 (21), and each channel was optimized separately. We found that optimizing each channel separately did not allow convergence to be achieved to a high enough accuracy for the majority of atoms, whereas optimization over all states provided reliable convergence.…”

Section: B Expansion In a Gaussian Basismentioning

confidence: 99%

“…We take the {a ql } parameters obtained from this least squares procedure as a starting point for a second stage of optimization. Here we employ a generalization of an algorithm developed by Barthelat et al 29 To progress further we perform a HF atomic calculation with LS coupling and using the tabulated pseudopotential V p,loc l , yielding the pseudo-states {φ p l ,ǫ p l }. For a given set of parameters for each channel, we also perform a similar HF atomic calculation using the parameterized pseudopotentialṼ p l , to give the pseudo-states {φ p l ,ǫ p l }.…”

Section: B Expansion In a Gaussian Basismentioning

confidence: 99%

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Smooth relativistic Hartree–Fock pseudopotentials for H to Ba and Lu to Hg

Trail

Needs

2005

The Journal of Chemical Physics

172

119

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We report smooth relativistic Hartree-Fock pseudopotentials (also known as averaged relativistic effective potentials or AREPs) and spin-orbit operators for the atoms H to Ba and Lu to Hg. We remove the unphysical extremely non-local behaviour resulting from the exchange interaction in a controlled manner, and represent the resulting pseudopotentials in an analytic form suitable for use within standard quantum chemistry codes. These pseudopotentials are suitable for use within Hartree-Fock and correlated wave function methods, including diffusion quantum Monte Carlo calculations.PACS numbers: 71.15. Dx, 02.70.Ss Pseudopotentials or effective core potentials (ECPs) are commonly used within electronic structure calculations to replace the chemically inert core electrons. The influence of the core on the valence electrons is then described by an angular-momentum-dependent effective potential, leading to greatly improved computational efficiency in ab initio calculations for heavy atoms. The use of pseudopotentials is well established within HartreeFock (HF) and Density Functional Theory (DFT), and in correlated wave function calculations.Our main interest is in diffusion quantum Monte Carlo (DMC) calculations. 1,2 This technique provides an accurate solution of the interacting electron problem for which the computational effort scales with the number of electrons, N , as approximately N 3 , which is better than other correlated wave function approaches. Unfortunately, scaling with atomic number, Z, is approximately 3,4 Z 5−6.5 . The use of a pseudopotential reduces the effective value of Z, making DMC calculations feasible for heavy atoms.There is evidence that HF pseudopotentials give better results within DMC than DFT pseudopotentials. 5 It appears that the complete neglect of core-valence correlation within HF theory leads to better pseudopotentials than the description of core-valence correlation provided by DFT. Moreover, core-valence correlation can be included within correlated wave function calculations performed with HF pseudopotentials by using core polarization potentials. 6,7,8 Core polarization potentials mimic the effects of dynamical polarization of the core by the valence electrons, as well as static polarization effects due to the other ions. We would therefore like to use HF pseudopotentials in our DMC calculations, preferably constructed from Dirac-Fock (DF) theory in order to include the relativistic effects which are significant for heavy atoms.Standard quantum chemistry packages are convenient for generating the "guiding wave functions" required in DMC calculations. We would therefore like our pseudopotentials to be available in the standard parameterized form of a sum of Gaussian functions multiplied by powers of the electron-nucleus separation.Extensive sets of parameterized pseudopotentials are available in the literature, but they have generally been constructed with different goals to ours. Relativistic pseudopotentials 9 generated within DFT and the local density approximation have be...

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Section: Discussionmentioning

confidence: 99%

Section: B Expansion In a Gaussian Basismentioning

confidence: 99%

Section: B Expansion In a Gaussian Basismentioning

confidence: 99%

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Smooth relativistic Hartree–Fock pseudopotentials for H to Ba and Lu to Hg

Trail

Needs

2005

The Journal of Chemical Physics

172

119

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“…The analytic Gaussian expansions used for these pseudopotentials generally contain a small number of terms, due to the limited amount of data being fit. The Durand/Barthelat potentials were also optimized by comparing ECP and all-electron calculations, but a unique functional based on orbital overlap and eigenvalue differences was used (16). The optimized RCEP parameters reported in this paper were determined by the same method.…”

Section: Primed In Canadamentioning

confidence: 99%

Relativistic compact effective potentials and efficient, shared-exponent basis sets for the third-, fourth-, and fifth-row atoms

Stevens¹,

Krauß²,

Basch³

et al. 1992

Can. J. Chem.

2,099

1,289

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. Can. J. Chem. 70, 6 12 (1992). Relativistic compact effective potentials (RCEP), which replace the atomic core electrons in molecular calculations, have been derived from numerical Dirac-Fock atomic wavefunctions using shape-consistent valence pseudo-orbitals and an optimizing procedure based on an energy-overlap functional. Potentials are presented for the third-, fourth-, and fifthrow atoms of the Periodic Table (excluding the lanthanide series). The efficiency of molecular calculations is enhanced by using compact Gaussian expansions (no more than three terms) to represent the radial components of the potentials, and energy-optimized, shared-exponent, contracted-Gaussian atomic orbital basis sets. Transferability of the potentials has been tested by comparing calculated atomic excitation energies and ionization potentials with values obtained from numerical relativistic Hartree-Fock calculations. For the alkali and alkaline earth atoms, core polarization potentials (CPP) have been derived which may be added to the RCEP to make possible accurate molecular calculations without explicitly including core-valence correlating configurations in the wavefunction. Introduction two rows (Li-Ar) of the Periodic Table ( 5 ) . We designatedThe use of atomic effective core potentials (ECP) and model potentials (MP) to eliminate chemically inactive atomic core electrons from quantum mechanical calculations has become routine in the past decade. The development of such potentials in the early 1970's and applications through the mid-1980's have been reviewed previously (1). The use of such potentials in molecular calculations has gained widespread acceptance, and sets of effective potentials are included in widely distributed quantum chemistry programs such as HONDO ( 2 ) , GAMESS (3), and GAUSSIAN (4). We previously published accurate compact effective potentials (CEP) and matching basis sets for the atoms of the first '~u t h o r to whom correspondence may be addressed. 'NRC-NAS Postdoctoral Fellow, NIST, 1984NIST, -1986. Current address: California State University, San Marcos, CA 92096, U.S.A.Primed in Canada -the potentials "compact" because they are represented analytically by small Gaussian expansions and, therefore, offer significant economy in molecular calculations where the computer time required to construct the electronic integrals is proportional to the complexity of the potentials. In this report, we present effective potentials and basis sets of similar quality for the third, fourth, and fifth rows of the Periodic Table derived from numerical, relativistic, Dirac-Fock atomic wavefunctions. The analytic expansions of these POtentials are also limited to a few Gaussian terms (three or less), so we have designated them as "relativistic compact effective potentials" (RCEP).Recently, several compilations of model potentials and effective core potentials for use in molecular calculations have appeared in the literature. For the heavier atoms, relativistic effects have been incorporated by deriving the potentials ...

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“…45͒ code was used with normconserving Durand-Barthelat 46 pseudopotentials and a 21G * valence basis 47 optimized for these pseudopotentials. Like in SIESTA, the Ceperley-Alder exchange-correlation functional in the Perdew-Zunger parametrization was used, with the exchange part mixed with exact exchange following the equation…”

Section: B Calculation Proceduresmentioning

confidence: 99%

Theoretical study of the mechanism of dry oxidation of4H-SiC

et al. 2005

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Possible defect structures, arising from the interaction of O 2 molecules with an ideal portion of the SiC/ SiO 2 interface, have been investigated systematically using density functional theory. Based on the calculated total energies and assuming thermal quasiequilibrium during oxidation, the most likely routes leading to complete oxidation have been determined. The defect structures produced along these routes will remain at the interface in significant concentration when stopping the oxidation process. The results obtained for their properties are well supported by experimental findings about the SiC/ SiO 2 interface. It is found that carbon-carbon bonds can explain most of the observed interface states but not the high density near the conduction band of 4H-SiC.

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Non-empirical pseudopotentials for molecular calculations

Cited by 335 publications

References 9 publications

Smooth relativistic Hartree–Fock pseudopotentials for H to Ba and Lu to Hg

Smooth relativistic Hartree–Fock pseudopotentials for H to Ba and Lu to Hg

Relativistic compact effective potentials and efficient, shared-exponent basis sets for the third-, fourth-, and fifth-row atoms

Theoretical study of the mechanism of dry oxidation of4H-SiC

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