Massimo Ottonelli

DIPOLE POLARIZABILITY PSEUDOSPECTRA AND C6 DISPERSION COEFFICIENTS FOR H2+-H2+

Abstract Pseudostate decomposition of static dipole polarizabilities for ground state H 2 + from a Givens-Householder diagonalization of the excitation operator ( H 0 − E 0 ) over an N -term basis of appropriate symmetry allows for a rapidly convergent evaluation of C 6 dispersion coefficients for H 2 + –H 2 + . 27-term pseudospectra of hypergeneralized James functions with a 30-term GGJ + unperturbed wavefunction with an optimized scale factor δ=0.918 at R =2α 0 give C 6 and γ 6 values that are accurate to no less than nine significant figures.

Accurate evaluation of C6 dispersion coefficients for (H2)2

Abstract The pseudostate decomposition of accurate Kolos-Wolniewicz static dipole polarizabilities for ground-state H 2 allows an extremely accurate evaluation of C 6 dispersion coefficients for (H 2 ) 2 .

Long-range dispersion coefficients for like centrosymmetric linear molecules and an application to H2H2

Abstract The real spherical tensor theory of long-range intermolecular coefficients developed in previous papers is applied to derive explicit formulae for the first three dispersion coefficients for like centrosymmetric linear molecules. The expansion of angledependent coefficients in associated Legendre polynomials allows one to identify the isotropic and anisotropic components of the dispersion interaction in terms of London dispersion constants, the treatment of higher coefficients being simplified by the coupling of the elementary (1, 1′)-polarizations to resultant angular momenta LA and LB onto each molecule. The contributions from all coupling schemes are given explicitly for C6, C8, c10, and numerical results are presented for H2H2 using two-term reduced spectra values from the Kaiserlautern group.

One-centre Gaussian linear pseudostate evaluation of dispersion coefficients between ground-state H atoms

Abstract One-centre Gaussian linear pseudostate evaluation of polarizabilities and dispersion coefficients for ground-state H atoms is seen to converge rapidly to accurate results which sensibly improve the corresponding optimized non-linear pseudostate calculations. The residual error is inherent to the GTO approximation of the unperturbed wavefunction.

Dipole polarizability pseudospectra and C6 dispersion coefficients for two-electron model systems

Abstract Convergence of dipole pseudospectra for the 2-electron model systems He and H 2 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 H 2 give almost a 4-figure accuracy for the static polarizabilities of the monomers and the resulting C 6 dispersion coefficients of the dimers.

DIPOLE POLARIZABILITIES AND C6 DISPERSION COEFFICIENTS FOR SMALL ATOMIC AND MOLECULAR SYSTEMS

Abstract An accurate evaluation of C 6 dispersion coefficients for long-range interactions involving H, He, H 2 + and H 2 has been performed using the London formula in terms of ab initio pseudostate decomposition of the static dipole polarizabilities of the individual atoms and molecules.

Long-range induction coefficients for like centrosymmetric linear molecules and an application to H2–H2

Abstract The C 8 and C 10 long-range induction coefficients for two like centrosymmetric linear molecules are derived explicitly using the irreducible properties of spherical tensor operators. An application to the H 2 –H 2 system shows that whereas the isotropic induction coefficients are 50–100 times smaller than dispersion, the induction anisotropies γ n are always larger than the corresponding dispersion anisotropies.

A simple and fast method for evaluating the athermal limit of semirigid liquid polymers

A simple method is reported allowing the fast evaluation of the athermal limit that is implicitly present within the set of equations recently proposed by Jonah, Brostow and Hess, dealing with the anisotropic-isotropic equilibria of single monodisperse or nearly monodisperse semirigid liquid polymers, including polymer liquid crystals. We have found an athermal limit dependent on the degree of rigidity 0 of the given semirigid liquid polymer (θ being the fraction of its monomeric units belonging to rigid rodlike sequences within each semiflexible polymeric chain) and marked off by critical lengths η al of the rigid sequences, giving rise to non-finite asymptotic values of the anisotropic-isotropic temperatures.

LONG-RANGE DISPERSION AND INDUCTION COEFFICIENTS FOR THE HOMODIMERS OF LI2, NA2 AND K2

Abstract Long-range dispersion and induction coefficients for the homodimers of Li2, Na2, K2 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.

PARTITIONED ORBITALS FOR THE PERTURBATIVE EVALUATION OF GROUND STATE HYDROGEN ATOM INDUCTION ENERGIES

A 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.