Université de Fribourg

Parallel algorithm for the computation of the Hartree-Fock exchange matrix: Gas phase and periodic parallel ONX

Weber, Valéry ; Challacombe, Matt

In: The Journal of Chemical Physics, 2006, vol. 125, p. 104110

In this paper we present an efficient parallelization of the ONX algorithm for linear computation of the Hartree-Fock exchange matrix [J. Chem. Phys. 106, 9708 (1997)]. The method used is based on the equal time (ET) partitioning recently introduced [J. Chem. Phys. 118, 9128 (2003)] and [J. Chem. Phys. 121, 6608 (2004)]. ET exploits the slow variation of the density matrix between...

Université de Fribourg

Energy gradients with respect to atomic positions and cell parameters for the Kohn-Sham density-functional theory at the Γ point

Weber, Valéry ; Tymczak, Christopher J. ; Callacombe, Matt

In: The Journal of Chemical Physics, 2006, vol. 124, p. 224107

The application of theoretical methods based on density-functional theory is known to provide atomic and cell parameters in very good agreement with experimental values. Recently, construction of the exact Hartree-Fock exchange gradients with respect to atomic positions and cell parameters within the Γ-point approximation has been introduced [V. Weber et al., J. Chem. Phys. 124, 214105...

Université de Fribourg

Exchange energy gradients with respect to atomic positions and cell parameters within the Hartree-Fock Γ-point approximation

Weber, Valéry ; Daul, Claude A. ; Challacombe, Matt

In: The Journal of Chemical Physics, 2006, vol. 124, p. 214105

Recently, linear scaling construction of the periodic exact Hartree-Fock exchange matrix within the Γ-point approximation has been introduced [J. Chem. Phys. 122, 124105 (2005)]. In this article, a formalism for evaluation of analytical Hartree-Fock exchange energy gradients with respect to atomic positions and cell parameters at the Γ-point approximation is presented. While the...

Université de Fribourg

Higher-order response in [script O](N) by perturbed projection

Weber, Valéry ; Niklasson, Anders M. N. ; Challacombe, Matt

In: The Journal of Chemical Physics, 2005, vol. 123, p. 044106

Perturbed projection for linear scaling solution of the coupled-perturbed self-consistent-field equations [V. Weber, A.M.N. Niklasson, and M. Challacombe, Phys. Rev. Lett. 92, 193002 (2004)] is extended to the computation of higher-order static response properties. Although generally applicable, perturbed projection is further developed here in the context of the self-consistent first and second...

Université de Fribourg

Improved coupled perturbed Hartree–Fock and Kohn–Sham convergence acceleration

Weber, Valéry ; Daul, Claude A.

In: Chemical Physics Letters, 2003, vol. 370(1-2), p. 99-105

A derivative version of the well-known direct inversion in the iterative subspace (DIIS) algorithm is presented. The method is used to solve the coupled perturbed Hartree–Fock (CPHF) equation to obtain the first and second derivatives of the density matrix with respect to an external electric field which, in this case, leads to the electric molecular polarizability and hyperpolarizability. Some...

Université de Fribourg

Investigation of NLO properties of substituted (M)-tetrathia-[7]-helicenes by semiempirical and DFT methods

Daul, Claude A. ; Ciofini, Ilaria ; Weber, Valéry

In: International Journal of Quantum Chemistry, 2003, vol. 91, no. 3, p. 297-302

In this article, we propose a theoretical study of static and dynamic polarizability α, first hyperpolarizability β, and second hyperpolarizability γ of substituted (M)-tetrathia-[7]-helicenes. Both a semiempirical approach, in the case of static and dynamic properties, and density functional theory, in the case of static electric properties, were used. The nonlinear optical (NLO) properties...

Université de Fribourg

Evaluation of two-electron integrals including the factors rk₁₂exp(−γr²₁₂) over Cartesian Gaussian functions

Weber, Valéry ; Daul, Claude A.

In: Computer Physics Communications, 2004, vol. 158 (1), p. 1-11

We present a practical scheme for the evaluation of nonstandard two-electron integrals including the factors rk₁₂exp(−γr²₁₂) which have been appeared recently, where k>=-1 is an integer. The method used throughout this paper is based on the highly efficient Head-Gordon and Pople (HGP) approach of evaluation of electron repulsion integrals (ERI). Thus only straightforward...

Université de Fribourg

Radial numerical integrations based on the sinc function

Weber, Valéry ; Daul, Claude A. ; Baltensperger, Richard

In: Computer Physics Communications, 2004, vol. 163(3), p. 133-142

An algorithm for the generation of adaptive radial grids used in density functional theory or quantum chemical calculations is described. Our approach is general and can be applied for the integration over Slater or Gaussian type functions with only minor modifications. The relative error of the integration is fully controlled by the algorithm within a specified range of exponential parameters...