W. England

Abinitio vertical spectra and linear bent correlation diagrams for the valence states of CO2 and its singly charged ions

Correlated and uncorrelated ab initio vertical spectra are reported for the valence states of CO2, CO2+, and CO2−. Calculations with polarized and unpolarized basis sets are compared at each level. Ground state quadrupole moments are computed. Linear molecule to bent molecule SCF correlation diagrams are also reported.

Theoretical studies of atmospheric triatomic molecules: Accurate SCF vertical spectrum for valence, mixed character, and Rydberg states of CO2

An accurate SCF vertical spectrum is computed for CO2. Orbital sizes, electric quadrupole moments, and quantum defects are reported for the excited states. The Rydberg MO expectation values are found to be highly transferable. Spectral assignments are made for the Rydberg states based on the closeness of agreement with observed spectroscopic data.

A theoretical study of Li2H. I. Basis set and computational survey of excited states and possible reaction paths

SCF potential curves for C2v (Li2+H) and C∞v (LiH+Li) symmetries have been calculated for the 26 lowest lying states of Li2H. The curves are estimated to be ≲0.1 eV above the Hartree–Fock–Roothaan limit. Correlated MCSCF/CI curves were computed for the lowest states of 2A1, 2B2, and 2Σ symmetries. All low‐lying states of the complex Li2H involve substantial charge transfer. The most stable of these, 2A1, lies ∼20 kcal/mole below the ground state LiH+Li asymptote. The first excited state of the complex, 2B2, is but weakly bound relative to the same asymptote. Electron‐jump geometries and vertical spectra were computed for all of these low‐lying states. Possible low‐energy paths for the reaction Li2+H→LiH+Li were determined, and all involve charge‐transfer intermediates.

Theoretical studies of atmospheric triatomic molecules: Abinitio equations of motion excitation energies for valence states of the configuration 1π3g2π1u in CO2

Polarized and unpolarized basis set equations‐of‐motion vertical spectra are presented for the five lowest valence states of CO2. In addition to the traditional solution method, an iterative diagonalization scheme is used to solve the renormalized matrix equations. The equations‐of‐motion methods depend on the basis set in much the same fashion as conventional SCF, MCSCF, and CI methods. The iterative diagonalization changes the excitation energies by ∼0.2 eV. The final polarized basis spectrum is the most accurate available for CO2.

The anisotropic interaction between hydrogen molecules

The extent to which it is possible to estimate the anisotropic potential between two hydrogen molecules directly from ab initio calculations of the short range repulsive part of the interaction potential and the available semiempirical van der Waals and quadrupolar potentials is investigated. The anisotropic potential parameters e0(R), e2(R), e4(R), and B (R) due to nonquadrupolar anisotropic interactions are estimated for hydrogen in the range of intermolecular separations from 2.5 to 5 A. At the nearest neighbor distance in solid hydrogen, R0=3.756 A, we recommend the following values e0=−0.002 cm−1, e2=−0.027 cm−1, e4=−0.016 cm−1, and B=−0.310 cm−1. At the next nearest neighbor distance of √2 R0, we suggest e0=−0.0011 cm−1, e2=−0.0017 cm−1, e4=−0.0029 cm−1, and B=−0.131 cm−1.

Rotational motion under pressure in the solid molecular hydrogen isotopes

Rotational states as functions of pressure for H2, D2, T2 HD, and HT molecules are calculated in the corresponding molecular solids. Sudden transitions from spherically symmetric rotational states occur in para-H2, para-T2, ortho-D2, and in HD and HT as the pressure increases. Only the predicted T2 transition pressure of about 24 kbar lies within current experimentally accessible ranges. All other transitions occur in the region 150–300 kbar.

Theoretical studies of MHD plasma molecules. I. Potential energy curves and dipole moments of linear KOH

Uncorrelated and correlated potential energy curves and dipole moments are reported for linear KOH. The compound is found to be ionic, K+OH−. Minimum energy bond lengths are RKO=4.2913 au and ROH=1.7688 au, with an estimated accuracy of 2%. The corresponding dipole moment is 3.3 au (8.46 D) with a similar accuracy estimate. This is to our knowledge the first value ever reported for the KOH dipole moment, and the large value suggests that KOH will be an effective electron scatterer in MHD plasmas.

Theoretical studies of atmospheric molecules: SCF and correlated energy levels for the NO2, NO 2 + and NO 2 ? systems

SCF and MC-SCF/CI calculations were carried out on the low-lying electronic states of NO2, NO2+ and NO2−, using a double-zeta quality basis set of contracted Gaussian functions. The calculations were performed primarily at the equilibrium geometry (RNO = 2.25 ao, θONO=134 °) of theX2A1 state of NO2. SCF calculations on NO2+ in a linear conformation were also performed. Results are presented and compared with experiment and other calculations.

Anisotropic contributions to the ground-state properties of solid para-H2

The local field approximation is modified so that the translational and rotational degrees of freedom of the H2 molecule are treated on an equal basis, when calculating the equation of state for solid para-H2. Near normal vapor pressure the anisotropies in the H2 pair interaction are found to make a negligible contribution to the binding energy and the equation of state, but that contribution increases with increasing pressure. However, the isotropic part of the potential plays the dominant role in determining the equation of state at all molar volumes investigated 3⩽V⩽22.65 cm3/mole. At extremely high pressures the results tend toward previous findings that were based upon a frozen P42/mnm (γ-N2) orientational structure.