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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1987

On the 3d6 4s2 (5D) - 3d7 4s1 (5F) separation in Fe

Full CI calculations are used to calibrate SDSI treatment of the 5D-5F separation in the Fe atom. The (5s4p2d), (5s4p3d), and (5s4p2d1f) basis sets were used for the FCI calculations. The importance of the 3s and 3p correlation and the relativistic effects are studied at SDCI level. The role of polarization functions in computing atomic separations in transition metal atoms is discussed. It is observed that the FCI separation is slightly smaller than the SDCI results, and the SDCI data yield an adequate description of the 5D-5F separation with only 8 electrons correlated. It is concluded that the differential effect of higher excitations becomes more important when the 3s and 3p electrons are correlated.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1980

On the 3d2 4s2, 3d3 4s1, and 3d4 states of Ti

The energies of the 3F (3d2 4s2), 5F (3d3 4s1) and 5D (3d4) states of Ti are investigated on the basis of MCSCF and CI calculations. Following SCF calculations using a basis set including the primitive set of Wachters (1970) and the diffuse d function of Hay (1977), four full-electron CI calculations involving the 3d and 4s electrons were performed to obtain the natural orbitals, and the full CI calculations were repeated. MCSCF calculations then performed using the most important configurations of the natural orbital basis are found to be in agreement with those of Dunning (1980), but to differ from CI results. CI(SD) calculations including single and double excitations from the MCSCF reference are found to be in agreement with the full CI but differ from experimental energy separations. Further calculations reveal that Dunning's MCSCF description is an oversimplication of the problem, and that the 5F-5D separation at the CI(SD) level is in good agreement with experiment for all basis sets but the 3F state is too low relative to the 5F and 5D states.

Bauschlicher, C. W., Jr.↗