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On the principle of maximum overlap in valence bond theory
No full textRevisitation of the Heitler–London theory for H2 shows that the exchange-overlap component of the bond energy has a strength which is maximum at the bond length. Making the usual assumptions typical of elementary Hückel theory including overlap it is similarly found that in the valence bond description of the chemical bond covalent bonding is strongest for atomic orbitals maximizing the strength of the complete exchange-overlap component of the bond energy
Dipole polarizability pseudospectra and C6 dispersion coefficients for two-electron model systems
No full textConvergence of dipole pseudospectra for the 2-electron model systems He and H2 is studied for Riley-Dalgarno- and Kolos-Wolniewicz-type wavefunctions explicitly including electron correlation in terms of positive powers of the interelectronic distance. 40-term pseudospectra for He and 34-term for H2 give almost a 4-figure accuracy for the static polarizabilities of the monomers and the resulting C6 dispersion coefficients of the dimers
Dipole polarizability pseudospectra and C 6 dispersion coefficients for H 2 + –H 2 +
No full textPseudostate decomposition of static dipole polarizabilities for ground state H2/+ from a Givens-Householder diagonalization of the excitation operator (H0 - E0) over an N-term basis of appropriate symmetry allows for a rapidly convergent evaluation of C6 dispersion coefficients for H2/+- H2/+. 27-term pseudospectra of hypergeneralized James functions with a 30- term GGJ+ unperturbed wavefunction with an optimized scale factor δ = 0.918 at R = 2a0 give C6 and γ6 values that are accurate to no less than nine significant figures
Erratum: Full-CI calculation of imaginary frequency-dependent dipole-quadrupole polarizabilities of ground state LiH and the C7 dispersion coefficients of LiH-LiH.
No full textFull-CI calculations of frequency-dependent dipole polarizabilities of ground state LiH have been performed in the imaginary frequency range 0-20 a.u. using an extended set of 109 Gaussian type orbitals (GTOs). A 32-points Gauss-Legendre quadrature of the Casimir-Polder formula over imaginary frequencies allows calculation of the dipole dispersion constants for the LiH-LiH homodimer, from which isotropic C-6 and anisotropy gamma (6) dispersion coefficients are derived for the first tim
Erratum to: "Full-CI calculation of imaginary frequency-dependent dipole-quadrupole polarizabilities of ground state LiH and the C7 dispersion coefficients of LiH-LiH [Chem. Phys. Lett. 363 (2002) 540-543]
No full textPartitioned orbitals for the perturbative evaluation of ground state hydrogen atom induction energies
No full textA new method has been developed for the evaluation of damped multipole contributions to the second order perturbative energies induced by molecular potentials on the ground state of hydrogen atoms. It involves non-conventional discontinuous atomic orbitals partitioned in their radial dependence, giving rise, however, to continuous first-order wavefunctions with continuous first derivatives. Small bases consisting of partitioned orbitals have been found sufficient to yield nearly exact evaluations of the first multipole contributions to the secondorder H–H+ induction energy, over a wide range of internuclear distances. © 1998 Taylor & Francis Group, LLC
Long-range dispersion and induction coefficients for the homodimers of Li2, Na2 and K2
No full textLong-range dispersion and induction coefficients for the homodimers of Li-2, Na-2, K-2 are evaluated in the LALBM scheme using explicit formulae presented previously and numerical values of moments, polarizabilities and dispersion constants obtained from 2-term reduced spectra of the Kaiserslautern group. While induction coefficients are 5-8 times smaller than dispersion, induction anisotropies are always larger than the corresponding dispersion anisotropies for all homodimers
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