Journal of Computational Chemistry

doi: 10.1002/jcc.540040201pmid: N/A

Krauss, M.; Stevens, W. J.

doi: 10.1002/jcc.540040202pmid: N/A

A relativistic effective core potential (REP) has been generated for the uranium atom and used in self‐consistent‐field calculations of the A states of UH, UF, and their ions. Energy curves were calculated at the base configuration level which ensures the dissociating atoms are described by Hartree–Fock wavefunctions. The electronic bonding of these molecules is found to be similar to that of comparable alkaline–earth hydrides and fluorides. The uranium 6p, 6d, and 5f orbitals retain their atomic character but the orbitals extend into the bonding region and are distorted by overlap repulsion and electrostatic effects. Nonetheless, the atomic energetic coupling determines that low energy states will have the maximum spin multiplicity and maximum orbital angular momentum projection consonant with the charge‐transfer bonding.

Essén, Hanno

doi: 10.1002/jcc.540040203pmid: N/A

This article presents a general method and accurate algorithm for calculating the Cartesian coordinates (xa, ya, za) from an arbitrary triple of distances r(a,i), angles, θ(a,j,k), or dihedral angles ϕ(a,l,m,n), specifying the position of the nucleus a relative to nuclei i, ⃜, n with known Cartesian coordinates. There is a brief discussion of the requirements on the 3N‐6 geometric parameters in order for them to determine the shape of an N‐atomic molecule.

Skancke, Per N.

doi: 10.1002/jcc.540040204pmid: N/A

The conformational preferences of the molecule 1,4‐pentadien‐3‐one (divinylketone) have been studied by ab initio molecular orbital calculations and discussed in terms of interaction between molecular fragments. The calculations predict a molecular ground state having a fully coplanar s‐cis, s‐cis conformation. In addition, we find three other structures that represent local minima on the energy surface. These are a fully coplanar s‐cis, s‐trans form, and two nonplanar s‐trans, s‐trans forms having symmetries C2 and C1h, respectively. The energies of these forms relative to the ground state are 7.5, 19.2, and 35.9 kJ/mol, respectively. The coplanar s‐trans, s‐trans form represents a saddle point on the energy surface. All conformers and the saddle point have been completely geometry optimized by the gradient technique. For the ground state a complete in‐plane harmonic force field has been evaluated.

Zeiss, G. D.; Whitehead, M. A.

doi: 10.1002/jcc.540040205pmid: N/A

The standard deviation in reduced errors (SDRE) quantitatively measures the similarity between an approximate and exact wavefunction. It is the Euclidean distance between the vector of the one‐electron property expectation values calculated using the approximate and exact expectation values.

Rys, J.; Dupuis, M.; King, H. F.

doi: 10.1002/jcc.540040206pmid: N/A

Following an earlier proposal to evaluate electron repulsion integrals over Gaussian basis functions by a numerical quadrature based on a set of orthogonal polynomials (Rys polynomials), \documentclass{article}\pagestyle{empty}\begin{document} $$ (\eta \eta \parallel \eta \eta) = 2(\rho/\pi)^{1/2} \sum\limits_{\alpha = 1, N} I_x(u_{\alpha})I_{y}(u_{\alpha}) I_z(u_{\alpha})W_{\alpha} $$ \end{document} a computational procedure is outlined for efficient evaluation of the two‐dimensional integrals Ix, Iy, and Iz. Compact recurrence formulas for the integrals make the method particularly fitted to handle high‐angular‐momentum basis functions. The technique has been implemented in the HONDO molecular orbital program.

Dewar, Michael J. S.; Rzepa, Henry S.

doi: 10.1002/jcc.540040207pmid: N/A

MNDO calculations of heats of formation, dipole moments, ionization potentials, and structures are reported for a wide range of compounds containing chlorine in its characteristic valence state (ClI) and one or more of the elements H, B, Be, C, N, O, and F. The calculated errors in the heats of formation and the dipole moments are not significantly greater than those previously reported for compounds containing no chlorine. First vertical ionization potentials were on average 0.95 eV too high. The ordering of higher cationic states was found to be correct, even for species such as Cl2O, Cl2, and HOCl, where ab initio–Koopmans' theorem calculations predict the incorrect ordering. The calculated energies and geometries of compounds such as CIF3 are qualitatively incorrect, probably because of the lack of 3d atomic orbitals in the orbital basis set.

Bishop, David M.; Cartier, Alain

doi: 10.1002/jcc.540040208pmid: N/A

Derivatives, with respect to the symmetry coordinates, of the components of the dipole polarizabilities of HF, H2O, and CH4 are calculated using the Kirkwood method and a generalization of that method. The results for the bond‐stretching derivatives are in reasonable agreement with those found by finite field calculations; those for angle changes are of the correct sign, but their magnitudes are in poor agreement with the finite field ones. The results are also analyzed using a four‐parameter bond polarizability model.

Murthy, A. S. N.; Ranganathan, Shoba

doi: 10.1002/jcc.540040209pmid: N/A

CNDO/Force and compliance constant methods were applied to define general quadratic potential functions for F2CO and HCOF. A satisfactory set of compliants was obtained by suitably scaling down the stretching and stretch–stretch elements of the initial force constant matrix, evaluated by the CNDO/force approach, followed by fitting the compliants to available experimental data.

Strömberg, Ann; Gropen, Odd; Wahlgren, Ulf

doi: 10.1002/jcc.540040210pmid: N/A

Gaussian basis sets, consisting of 15 s‐type, 11 p‐type, and 6 d‐type functions, for the fourth‐row main group elements, In‐Xe, are presented. In order to compare these basis sets with larger ones, calculations have been performed in I2 and TeO2.