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Raffenetti, R. C.

Publications and source records attributed to Raffenetti, R. C..

5 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Gaseous NH4Cl revisited - A computational investigation of the potential surface and properties

An investigation of the potential surface and properties of the ground state of gaseous NH4Cl is presented. The calculations, which utilize a good basis set and include investigation of the valence correlation effects, result in a description of gaseous NH4Cl as a weakly bound complex with NH3 and HCl structures essentially equivalent to those of the isolated fragments. The charge distributions within the fragments are modifed in the complex, however, and there is a small amount of charge transfer. The results are in reasonable agreement with estimate of D sub 0, super 0 from high temperature mass spectroscopic investigations and vibrational frequencies from matrix experiments. The equilibrium constant for the reversible reaction NH4Cl yields NH3 + HCl indicates that the homogeneous formation of NH4Cl does not represent a significant chemical sink for HCl in the upper atmosphere

Raffenetti, R. C.↗
NASA NTRS1979

A simultaneous coordinate relaxation algorithm for large, sparse matrix eigenvalue problems

An algorithm is proposed for a scheme of simultaneous coordinate relaxation. A variant of root-shifting coordinate relaxation, this procedure consists of iterating several vectors at the same time, instead of one at a time. Results of application of the algorithm to test matrices are discussed. For many matrix eigenvalue problems for which coordinate relaxation is a viable approach, the present algorithm is more effective than previous implementations of coordinate relaxation. Total central processor operations should be decreased due to significantly improved convergence.

Raffenetti, R. C.↗
NASA NTRS1979

Ab initio studies of the electronic structure of UF6, UF6/+/, and UF6/-/ using relativistic effective core potentials

The paper presents ab initio calculations performed on the electronic states of UF6, UF6(+), and UF6(-) using a relativistic effective core potential (ECP) for uranium and a nonrelativistic ECP for fluorine. In most of the calculations 56 valence electrons are treated explicitly using a contracted (3s 3p 2d 2f/2s2p) Gaussian basis. It is noted that various ECP's were explored, but all yield an overall charge density of U(+2.4)/F(-0.4)/6. In addition, the bonding in the ground state of UF6 is discussed. SCF and CI calculations on UF6(+) are compared with the experimental photoelectron spectrum and with previous scattered wave calculations. Further, the role of spin-orbit coupling in the states of UF6(+) and UF6(-) is covered. Finally, it is concluded that the calculated electron affinity of UF6 (7.1 eV) is considerably larger than in current experimental estimates, but the relative energies of the states of UF6(-) are in agreement (0.1-0.2 eV) with those of the experiment.

Hay, P. J.↗
NASA NTRS1976

Electronic states of Zn2 - Ab initio calculations of a prototype for Hg2

The electronic states of Zn2 are investigated by ab initio polarization configuration-interaction calculations. Molecular states dissociating to Zn(1S) + Zn(1S, 3P, 1P) and Zn(3P) + Zn(3P) are treated. Important effects from states arising from Zn(+)(25) + Zn(-)(2P) are found in the potential-energy curves and electronic-transition moments. A model calculation for Hg2 based on the Zn2 curves and including spin-orbit coupling leads to a new interpretation of the emission bands in Hg vapor.

Hay, P. J.↗