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Partridge, Harry

Publications and source records attributed to Partridge, Harry.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Franck-Condon factors for photodetachment from LiO(-), NaO(-), and KO(-)

The 1Sigma(+), 3Sigma(+), 1Pi, and 3Pi states of the negative ions and the 2Pi and 2Sigma(+) states of the neutral alkali oxides are studied at high levels of theory. The calculations show that ground state of the negative ions changes from 3Pi for LiO(-) to 1Sigma(+) for KO(-). Although the calculations give a 3Pi ground state for NaO(-), we cannot rule out the possibility that the very low-lying 1Sigma(+) state is the true ground state. The Franck-Condon factors for photodetachment of an electron from the 1Sigma(+) and/or 3Pi states of the negative ion are presented to help interpret photodetachment experiments. Our best results for the A 2Sigma(+) - X 2Pi separations in LiO and NaO are 2496 and 2061/cm, which are in excellent agreement with that deduced (2516 and 2018/cm) from experiment.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1993

Theoretical study of the lowest 5Pi and 5Sigma(+) states of CO

Large one-particle basis sets and the internally contracted multireference configuration-interaction treatment of electron correlation were used to characterize the lowest 5Pi and 5Sigma(+) states of CO. It was found that the (1)5Sigma(+) state is weakly bound with an r(e) of 4.76 a(0), supporting results of calculations by Rosenkrantz et al. (1992). The (1)5Pi state has a weakly bound outer well and a significantly bound inner well.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1993

Relativistic Corrections to the Properties of the Alkali Fluorides

Relativistic corrections to the bond lengths, dissociation energies and harmonic frequencies of KF, RbF and CsF have been obtained at the self-consistent field level by dissociating to ions. The relativistic corrections to the bond lengths, harmonic frequencies and dissociation energies to the ions are very small, due to the ionic nature of these molecules and the similarity of the relativistic and nonrelativistic ionic radii.

Dyall, Kenneth G.↗
NASA NTRS1993

Tungsten hexahydride (WH6) - An equilibrium geometry far from octahedral

Ab initio all-electron quantum mechanical studies of the tungsten hexahydride molecule WH6 are reported. The results suggest that the ground state of WH6 molecule is a closed-shell triangular prism belonging to the C(3v) point group, with a set of three hydrogens stacked on top of another set of three hydrogens. The octahedral structure lies 130 kcal/mole above the C(3v) ground state, a remarkable result in inorganic chemistry. Another C(3v) structure, with one set of three hydrogens staggered with respect to the other set, is energetically nearby.

Shen, Mingzuo↗
NASA NTRS1993

Determination of the structure and bond energies of NiO2 and CuO2

On the basis of extensive ab initio calculations, we estimate the metal-O2 binding energies of NiO2 and CuO2 to be 48 +/- 7 and 18 +/- 4 kcal/mol, respectively. We feel that the experimental estimate of 57 +/- 10 kcal/mol for the binding energy of NiO2 is slightly too large, while we are in complete agreement with the experimental estimate of 15 +10/-5 kcal/mol for CuO2. While the 1A1 ground state of NiO2 definitely has a side-on C(2v) structure, matrix isolation studies suggest that CuO2 has an end-on C(s) structure. Calculations at the coupled-cluster singles plus doubles level with a perturbational estimate of triple excitations, CCSD(T), produce a 2A2 state with C(2v) as a global minimum. However, the entire 2A-double prime ground-state surface is exceedingly flat, precluding a reliable determination of the gas-phase equilibrium structure.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1992

A comparison of the coupled cluster and internally contracted averaged coupled-pair functional levels of theory for the calculation of the MCH2(+) binding energies for M = Sc to Cu

The correlation contribution to the M-C binding energy for the MCH2(+) systems can exceed 100 kcal/mol. At the self-consistent field (SCF) level, these systems can be more than 50 kcal/mol above the fragment energies. In spite of the poor zeroth-order reference, the coupled cluster single and double excitation method with a perturbational estimate of triple excitations, CCSD(T), method is shown to provide an accurate description of these systems. The maximum difference between the CCSD(T) and internally contracted averaged coupled-pair functional binding energies is 1.5 kcal/mol for CrCH2(+), with the remaining systems agreeing to within 1.0 kcal/mol.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1992

The 2Sigma(+)-2Pi separation in KO

The 2Sigma(+)-2Pi separation in KO is investigated using large basis sets and high levels of correlation treatment. Relativistic effects are included at the Dirac-Fock level and reduce the separation only slightly. The basis set superposition error is considered in detail. On the basis of these calculations, our best estimate places the 2Pi3/2 state about 200/cm above the ground 2Sigma(+) state, in agreement with our previous estimate.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1992

Calculation of Mg(+)-ligand relative binding energies

The calculated relative binding energies of 16 organic molecules to Mg(+) are compared with experimental results where available. The geometries of the ligands and the Mg(+)-ligand complexes arc optimized at the self-consistent field level using a 6-31G* basis set. The Mg(+) binding energies are evaluated using second-order perturbation theory and basis sets of triple-sigma quality augmented with two sets of polarization functions. This level of theory is calibrated against higher levels of theory for selected systems. The computed binding energies are accurate to about 2 kcal/mol.

Partridge, Harry↗
NASA NTRS1992

Theoretical study of hydrogen and nitrogen interactions - N-H transport cross sections and collision integrals

Potential energy curves have been calculated for the X 3Sigma(-) and 5Sigma(-) states of NH using a complete-active-space self-consistent-field/multireference configuration-interaction procedure and extensive Gaussian basis sets. An accurate dipole moment function is computed for the X 3Sigma(-) state. Transport cross sections have been calculated for the collisions of hydrogen and nitrogen atoms in their ground states. The mean transport cross sections are tabulated for collision energies in the range 0.0001-1 E(h); the mean collision integrals are listed for temperatures between 100 and 100,000 K. The ab initio energies for the 5 Sigma(-) state of NH are found to be consistent with the results of correlation studies and agree well with the prediction from combining relations using the energies of the highest spin states of H2 and N2.

Stallcop, James R.↗
NASA NTRS1992

Tables Of Gaussian-Type Orbital Basis Functions

NASA technical memorandum contains tables of estimated Hartree-Fock wave functions for atoms lithium through neon and potassium through krypton. Sets contain optimized Gaussian-type orbital exponents and coefficients, and near Hartree-Fock quality. Orbital exponents optimized by minimizing restricted Hartree-Fock energy via scaled Newton-Raphson scheme in which Hessian evaluated numerically by use of analytically determined gradients.

Partridge, Harry↗
NASA NTRS1992

Theoretical study of the 2A2-2B2 separation of the alkali superoxides

The computed 2A2-2B2 separations of the alkali superoxides are in good agreement with those deduced from electron-spin resonance spectra. The calculations definitively show that the ground state of CsO2 is 2A2. The larger than expected separation for CsO2, based on the trend from LiO2 to RbO2, is attributed primarily to the differential effects of core relaxation. The CsO2 dissociation energy is computed to be 42.7 kcal/mol, with an uncertainty conservatively estimated as +/- 4 kcal/mol.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1992

H-N2 interaction energies, transport cross sections, and collision integrals

The energies for the interaction of a hydrogen atom with a nitrogen molecule have been calculated for large separation distances using a complete-active-space self-consistent-field/externally contracted configuration interaction method. H-N2 transport cross sections and collision integrals have been calculated using sudden approximations and a semiclassical description of the scattering. The values of these quantities are found to be close to the corresponding values determined from the average (isotropic) potential energy. The collision integrals are applied to determine diffusion and viscosity coefficients; the theoretical diffusion agrees well with the measured data available from experiments at low temperatures.

Stallcop, James R.↗
NASA NTRS1992

Comparative study of the dissociation energies of Ni2 and Ni2(+)

Computations at the internally contracted averaged coupled-pair-functional level of theory yield a dissociation energy (Do) for Ni2(+) that is 0.17 eV larger than that of Ni2. This finding is consistent with the collision-induced dissociation experiments of Lian, Su, and Armentrout, but rules out the results from the resonant two-photon dissociation experiments of Lessen and Brucat, which predict that the Do value of Ni2(+) is about 1 eV larger than that of Ni2.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1992

Theoretical determination of the alkali-metal superoxide bond energies

The bond dissociation energies for the alkali-metal superoxides have been computed using extensive Gaussian basis sets and treating electron correlation at the modified coupled-pair functional level. Our computed D0 values are 61.4, 37.2, 40.6, and 38.4 kcal/mol for LiO2, NaO2, KO2, and RbO2, respectively. These values, which are expected to be lower bounds and accurate to 2 kcal/mol, agree well with some of the older flame data, but rule out several recent experimental measurements.

Partridge, Harry↗
NASA NTRS1992

A theoretical study of Mg(CO2)n(+) and Sr(CO2)n(+) for n = 1 and 2 and Mg2CO2(+)

The structure and binding energies are determined for Mg(CO2)n(+) and Sr(CO2)n(+) for n = 1 and 2. We also consider Mg2(+) and Mg2CO2(+) to compare the binding of CO2 to a single metal ion with the binding to a diatomic ion. The vertical excitation energies are computed for all species. The potential energy curves for the low-lying states of Mg2(+) are reported. The MgCO2(+) results are in good agreement with the experimental results of Duncan and co-workers.

Sodupe, Mariona↗
NASA NTRS1992

Theoretical study of transition-metal ions bound to benzene

Theoretical binding energies are reported for all first-row and selected second-row transition metal ions (M+) bound to benzene. The calculations employ basis sets of at least double-zeta plus polarization quality and account for electron correlation using the modified coupled-pair functional method. While the bending is predominantly electrostatic, the binding energies are significantly increased by electron correlation, because the donation from the metal d orbitals to the benzene pi* orbitals is not well described at the self-consistent-field level. The uncertainties in the computed binding energies are estimated to be about 5 kcal/mol. Although the calculated and experimental binding energies generally agree to within their combined uncertainties, it is likely that the true binding energies lie in the lower portion of the experimental range. This is supported by the very good agreement between the theoretical and recent experimental binding energies for AgC6H6(+).

Bauschlicher, Charles W., Jr.↗
NASA NTRS1992

Theoretical study of Cr(+) and Co(+) bound to H2 and N2

Binding energies of Co(H2)n(+) (n = 1-3) and CrN2(+) computed using the modified coupled-pair functional approach agree well with measured values. The calculations show that both H2 and N2 bond much more strongly to Co(+) than to Cr(+). Theoretical studies also show that despite the similar polarizabilities of N2 and Ar, the CrN2(+) binding energy is twice as large as that of CrAr(+) due to the charge-quadrupole contribution. Finally, the bonding of H2 and N2 with Na(+) and Mg(+) is contrasted with that for Cr(+) and Co(+).

Bauschlicher, Charles W., Jr.↗