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Partridge, Harry

Publications and source records attributed to Partridge, Harry.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Theoretical study of the NO beta system

A theoretical determination of the transition moment functions (TMFs) for the beta system of NO is presented. High levels of correlation treatment are required to show the changing degree of Rydberg character in the B2II with decreasing r values. The state-averaged complete-active-space self-consistent-field multireference configuration-interaction method is used for the determination. Previous lifetime measurements made with laser-induced fluorescence, varying between 2 and 0.85 microns, are discussed in terms of the calculated lifetimes for v-prime values 0-6, which vary from 2.12-1.17 microns. When larger r values are used for the transition moment function, the calculated lifetimes correlate with experimental lifetimes. The Einstein coefficients agree with experimental results, although limitations in the calibration of the spectrometer can account for systematic differences. The correlation with earlier experimental results suggests that radiative lifetimes are in the range of 1-2 microns.

Langhoff, Stephen R.↗
NASA NTRS1991

The binding energies of Cu(+)-(H2O)n and Cu(+)-(NH3)n (n = 1-4)

The successive binding energies of up to four H2O and NH3 ligands to Cu(+) are computed at the self-consistent-field and modified coupled-pair functional levels. The most stable structures are those where all ligands are equivalent. Replacing Cu(+) by a point charge gives binding energies that are in good agreement with ab initio and experimental results, and is consistent with bonding that is largely charge dipole in nature. About two-thirds of the large reduction in ligand binding energy between the second and third ligand is due to ligand-ligand repulsion, while one-third is due to increased metal-ligand repulsion resulting from a loss of sd-sigma hybridization. The first and second ligand binding energies increase substantially at the correlated level due to an improved description of sd-sigma hybridization.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1991

The bonding of multiple ligands to Mg(+) and Al(+)

The bonding of one to four waterligands to Mg(+) and Al(+) is studied. The bonding is very different from that found for multiple ligands bound to Na(+) or Cu(+). All the waters bind on the same side of the Mg or Al because of the polarization of the 3s orbital away from the ligands. Two benzene and methanol molecules also have a ligand-Mg-ligand angle of less than 180 deg with the angle determined by ligand-ligand repulsion.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1991

The 2S(+) - 2P separation in KO

The 2S(+) - 2P 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 2p sub 3/2 state about 200 cm(exp -1) above the ground 2 sigma(+) state in agreement with our previous estimate.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1991

Theoretical study of the spectroscopy of the alkali oxides LiO, NaO, and KO

A state-averaged complete-active-space self-consistent-field multireference configuration-interaction method is presented to characterize the bound-bound emission from the CPi-2 state into the two lowest ionic states of LiO, NaO, and KO. Ab initio calculations use the experimental results obtained by Woodward et al. (1989) of the emitting state as CPi-2, but indicate that the tentative experimental band assignments are incorrect.

Langhoff, Stephen R.↗
NASA NTRS1990

Theoretical study of the homonuclear tetramers and pentamers of the group IB metals (Cu, Ag, and Au)

The optimal structures of the homonuclear tetramers and pentamers of Cu, Ag, and Au are found to be planar trapezoidal. However, on the basis of spin densities deduced from electron spin resonance experiments, it has been suggested that these pentamers have distorted trigonal bipyramidal structures. This apparent discrepancy is reconciled by the fact that Mulliken populational analyses indicate that the open-shell spin density distribution on the planar structures are also consistent with experiment. Since the vertical electron attachment energies for both the tetramers and pentamers are in good agreement with experiment, the negative ions probably also have planar trapezoidal structures. The trends in ionization potentials, atomization energies, and electron affinities with cluster size are discussed.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1990

Theoretical study of the spectroscopy of NO(+)

The spectroscopy of the NO(+) molecule has been studied using multireference configuration-interaction calculations. The peak at 21.7 eV in the photoelectron spectrum of NO is assigned to the (2) 3Pi state (c 3Pi) and the vibrational progression centered at 23.1 eV is assigned to the diabatic (3) 1Pi state (B 1Pi). Several additional bound states with binding energies in excess of 1 eV are characterized in the present work. Radiative lifetimes are presented for many of the states.

Partridge, Harry↗
NASA NTRS1990

On the dissociation energy of Mg2

The bonding in the X 1Sigma(+)g state of Mg2 is investigated using near-complete valence one-particle Slater and Gaussian basis sets containing up to h functions. It is shown that the four-electron complete CI limit can be approached using a sequence of either second-order CI (SOCI) or interacting correlated fragment (ICF) calculations. At the valence level, the best estimate of the dissociation energy D(e) was 464/cm. This is a lower limit and is probably within 5/cm of the complete basis value.

Partridge, Harry↗
NASA NTRS1990

Comparison of the bonding between ML(+) and ML2(+) (M = metal, L = noble gas)

Ab initio calculations are reported of the spectroscopic constants for the low-lying states of the molecular ions ML2(+), where M = Li, Na, Mg, V, Fe, Co, Ni and Cu, and where L is usually Ar. Comparison with existing analogous calculations on the ML(+) ions shows how the bonding and binding energy change with the addition of a second noble gas atom. The second binding energy is predicted to be essentially the same as the first for the Li, Na, Mg, and V ions, but larger for the Fe, Co, Ni and Cu ions. The binding energies of the transition metal noble gas ions are not accurately predicted at the SCF level, because correlation is required to describe their M(0)Ln(+) character. All trends can be explained in terms of promotion and hybridization on the metal ion.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1990

All-electron molecular Dirac-Hartree-Fock calculations: The group 4 tetrahydrides CH4, SiH4, GeH4, SnH4 and PbH4

A basis-set-expansion Dirac-Hartree-Fock program for molecules is described. Bond lengths and harmonic frequencies are presented for the ground states of the group 4 tetrahydrides, CH4, SiH4, GeH4, SnH4, and PbH4. The results are compared with relativistic effective core potential (RECP) calculations, first-order perturbation theory (PT) calculations and with experimental data. The bond lengths are well predicted by first-order perturbation theory for all molecules, but non of the RECP's considered provides a consistent prediction. Perturbation theory overestimates the relativistic correction to the harmonic frequencies; the RECP calculations underestimate the correction.

Dyall, Kenneth G.↗
NASA NTRS1990

Theoretical studies of the first- and second-row transition-metal dimethyls and their positive ions

Equilibrium structures for the ground and the selected low-lying excited states of the first- and the second-row transition-metal dimethyls and their positive ions were determined using the basis sets and correlation approach described by Bauschlicher et al. (1989). In particular, the dimethyl insertion products were examined to elucidate the trends in bonding. Results show that the bonding in the dimethyl transition-metal positive ions arises from the sd hybridization, leading, for most dimethyls, to a C-M-C bond angle of less than 134 deg.

Rosi, Marzio↗
NASA NTRS1990

An Ab Initio Study of the Low-Lying Doublet States of AgO and AgS

Spectroscopic constants (D(sub o), r(sub e), mu(sub e), T(sub e)) are determined for the doublet states of AgO and AgS below approx. = 30000/cm. Large valence basis sets are employed in conjunction with relativistic effective core potentials (RECPs). Electron correlation is included using the modified coupled-pair functional (MCPF) and multireference configuration interaction (MRCI) methods. The A(sup 2)Sigma(sup +) - X(sup 2)Pi band system is found to occur in the near infrared (approx. = 9000/cm) and to be relatively weak with a radiative lifetime of 900 microns for A(sup 2)Sigma(sup +) (upsilon = 0). The weakly bound C(sup 2)Pi state (our notation), the upper state of the blue system, is found to require high levels of theoretical treatment to determine a quantitatively accurate potential. The red system is assigned as a transition from the C(sup 2)Pi state to the previously unobserved A(sup 2)Sigma(sup +) state. Several additional transitions are identified that should be detectable experimentally. A more limited study is performed for the vertical excitation spectrum of AgS. In addition, a detailed all-electron study of the X(sup 2)Pi and A(sup 2)Sigma(sup +) states of AgO is carried out using large atomic natural orbital (ANO) basis sets. Our best calculated D(sub o) value for AgO is significantly less than the experimental value, which suggests that there may be some systematic error in the experimental determination.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1989

Collision integrals and high temperature transport properties for N-N, O-O, and N-O

Accurate collision integrals are reported for the interactions of N(4 S 0) + N(4 S 0), O(3 P), and N(4 S 0) + O(3 P). These are computed from a semiclassical formulation of the scattering using the best available representations of all of the potential energy curves needed to describe the collisions. Experimental RKR curves and other accurate measured data are used where available; the results of accurate ab initio electronic structure calculations are used to determine the remaining potential curves. The high-lying states are found to give the largest contributions to the collision cross sections. The nine collision integrals, needed to determine transport properties to second order, are tabulated for translational temperatures in the range 250 K to 100,000 K. These results are intended to reduce the uncertainty in future predictions of the transport properties of nonequilibrium air, particularly at high temperatures. The viscosity, thermal conductivity, diffusion coefficient, and thermal diffusion factor for a gas composed of nitrogen and oxygen atoms in thermal equilibrium are calculated. It was found that the second order contribution to the transport properties is small. Graphs of these transport properties for various mixture ratios are presented for temperatures in the range 5000 to 15000 K.

Levin, E.↗
NASA NTRS1989

Theoretical study of metal noble-gas positive ions

Theoretical calculations have been performed to determine the spectroscopic constant for the ground and selected low-lying electronic states of the transition-metal noble-gas ions Var(+), FeAr(+), CoAr(+), CuHe(+), CuAr(+), and CuKr(+). Analogous calculations have been performed for the ground states of the alkali noble-gas ions LiAr(+), LiKr(+), NaAr(+), and KAr(+) and the alkaline-earth noble-gas ion MgAr(+) to contrast the difference in binding energies between the simple and transition-metal noble-gas ions. The binding energies increase with increasing polarizability of the noble-gas ions, as expected for a charge-induced dipole bonding mechanism. It is found that the spectroscopic constants of the X 1Sigma(+) states of the alkali noble-gas ions are well described at the self-consistent field level. In contrast, the binding energies of the transition-metal noble-gas ions are substantially increased by electron correlation.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1989

Theoretical studies of the first- and second-row transition-metal methyls and their positive ions

The metal-carbon bond-dissociation energies (D0) and geometries for the first- and second-row transition-metal methyl neutrals and positive ions are determined. The computed D0 values for the positive ions compare favorably with experiment, except for RuCH3(+), RhCH3(+), and PdCH3(+), where the experimental values are 10-15 kcal/mol larger. The computed D0 values for the hydride and methyl positive ions are similar for all metals in both transition rows, except for Cu and Ag. However, for the neutral systems, the D0 values for the methyls are smaller, especially on the right-hand side of both transition rows, where the differences approach 15 kcal/mol.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1989

Theoretical study of the structures and electron affinities of the dimers and trimers of the group IB metals (Cu, Ag, and Au)

The molecular structure of both the neutral and negatively charged diatomic and triatomic systems containing the Cu, Ag, and Au metals are determined from ab initio calculations. For the neutral triatomic systems, the lowest energy structure is found to be triangular. The relative stability of the 2A1 and 2B2 structures can be predicted simply by knowing the constituent diatomic bond distances and atomic electron affinities (EAs). The lowest energy structure is linear for all of the negative ions. For anionic clusters containing Au, the Au atom(s) preferentially occupy the terminal position(s). The EAs of the heteronuclear systems can be predicted relatively accurately from a weighted average of the corresponding homonuclear systems. Although the theoretical EAs are systematically too small, accurate predictions for the EAs of the triatomics are obtained by uniformly scaling the ab initio results using the accurate experimental EA values available for the atoms and homonuclear diatomics.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1989

The dissociation energy of He2(+)

Ab initio potential energy curves for He2(+) are computed using full CI wavefunctions in conjuction with large Gaussian and Slater basis sets. The computed curves yield rotational-vibrational transitions with errors of less than 1/cm. They also yield quasi-bound levels with energies and lifetimes in reasonable agreement with translational spectroscopy measurements. The best D(e) is estimated to be 2.470 eV. Green's function Monte Carlo calculations yield a very similar value, 2.466 + or - 0.005.

Bauschlicher, Charles W., Jr.↗