A discussion of general-purpose computer programs in theoretical chemistry is given, followed by a description of the procedures adopted in one such program written by the authors. Specific details on the use of the program for computing molecular wave functions and properties for closed-shell linear molecules are presented. The details of a method for computing the axial components of the static electric polarizability and shielding factor tensors are given. A "Table of Linear Molecule Wave Functions" is available, on request to the authors, as a supplement to the paper. This tabulation was made with the program described in the paper and is the most extensive compilation of molecular wave functions currently available.

Computation of molecular properties and structure

The effect of various possible contractions of a gaussian basis set is investigated for atomic and molecular calculations. The gaussian basis set used consists of 11s-type functions and 7p-type functions. Atomic calculations for the atoms Li to F are reported with fourteen different contractions of the s orbitals. The effect of the same contractions has also been investigated for molecular calculations of LiH, BH, CH2, NH
 2
 −
 , H2O, and FH, together with the effect of the contraction for the p orbitals and for the s orbitals of the hydrogen atom. It is shown that the contraction in itself does not affect seriously the quality of a molecular calculation, but that a wrong choice of the contraction can produce a poor result.

A comparison of different contractions for molecular calculations with gaussian-type functions

A systematic study of the electronic structure and chemical binding in the dimer ion sequence, Ne2+, Ar2+, Kr+2, and Xe2+, has been carried out using density functional methods. For comparison, ab initio configuration‐interaction calculations were also performed for the Ar2+ ion. These studies include detailed calculations of the pertinent potential energy curves and an analysis of the calculated spectroscopic properties of the bound states of these ions. A regular progression is found in the spectroscopic properties for the ground A 2Σ+1/2u state which leads to some remarkably simple conclusions concerning the nature of the binding and the size of these dimer ions. For the heavier systems, Kr2+ and Xe+2, spin–orbit coupling becomes important, resulting in a strong mixture of the Λ–S coupled Σ and Π states. This mixing affects the strength of the binding in the ground state. A comparison with other ab initio studies and an analysis of the asymptotic behavior at large internuclear separations is given. The...

Electronic structure of the noble gas dimer ions. I. Potential energy curves and spectroscopic constants

Using the optimized valence configurations (OVC) multiconfiguration self-consistent-field (MCSCF) method, the dipole moment function for the ground state of CO in the vicinity of the equilibrium internuclear distance has been calculated. The OVC MCSCF calculation results are compared with existing Hartree-Fock and configuration interaction treatments of this molecule at single points and also the dipole moment function deduced from experimental infrared intensities. A general prescription for constructing OVC wavefunctions for diatomic molecules is also presented.

Multiconfiguration self-consistent-field calculation of the dipole moment function of CO/X 1 sigma +/

State-selected ion-molecule reactions: N2+(X, v″), N2+(A, v′) + Ar → N2 + Ar+

: The number of ab initio molecular electronic calculations has increased dramatically in the last few years. Both the practitioners and other interested students of the results of the calculations have found it increasingly difficult to determine the present status of these calculations. This compendium references the work from 1960 to the present and abstracts from the mass of data the best values for several observable properties including the total energy, dissociation energy, electron affinity, spectroscopic constants, electric moments, field gradients, polarizabilities, and magnetic constants. In order to provide an insight into molecular electronic structure tables of orbital energies are also included. These tables are meant to direct attention to the successes and failures of the calculations by compiling a large percentage of the best results in a reasonably compact form. Its usefulness will be limited in time by rapid advance in the field. (Author)

Morris Krauss

Papers

Compendium of AB Initio Calculations of Molecular Energies and Properties