Dean H. Liskow

Model studies of chemisorption. Interaction between atomic hydrogen and beryllium clusters

The interaction between hydrogen atoms and Be metal clusters has been studied by ab initio electronic structure theory. Self‐consistent‐field (SCF) calculations have been carried out using both minimum and larger basis sets of contracted Gaussian functions. Both spatially restricted and unrestricted SCF methods were used, and different results were obtained in several cases. Reasons for the choice of this particular model system are discussed. Clusters as large as ten Be atoms have been considered, as have four different sites for the approach of the H atom. The electronic structure is discussed on the basis of predicted orbital energies and Mulliken atomic populations.

Potential energy surfaces related to the ion‐molecule reaction C+ + H2

The C+ + H2 ion‐molecule reaction has been studied by several experimental groups and appears likely to become the focal point of much experimental and theoretical activity. Ab initio self‐consistent‐field and configuration interaction calculations have accordingly been carried out for this system. A double zeta basis set of contracted Gaussian functions was employed and as many as 648 configurations included. For isosceles triangle configurations (C2V point group) the 2A1, 2B1, and 2B2 potential surfaces were considered, while for linear geometries (C ∞V) the 2Σ+ and 2Π surfaces were studied. For general (Cs) geometry, the lowest 2A′ potential surface was considered. Properties reported include minimum energy paths and energy profiles for the various processes considered. The intuitive correlation diagram of Mahan and Sloane is given qualitative reliability. Pathways to CH2+ complex formation are shown to depend crucially on the Cs potential surface.

Some Features of the CH3NC→CH3CN Potential Surface

Nonempirical self‐consistent‐field calculations are reported for about 75 points on the potential surface for the CH3NC→CH3CN isomerization. Due to interest in the possible non‐RRKM behavior of CH3NC, the magnitude of the barrier to rotation of the methyl group is examined as a function of the reaction coordinate. The transition state or saddle point geometry is determined by minimizing the potential energy with respect to five geometrical parameters and maximizing with respect to a sixth. The geometries of CH3NC and CH3CN are also predicted and found to agree closely with experiment. Finally, it is established that, contrary to semiempirical results, the present theoretical approach does not predict the existence of a relative minimum in the reaction coordinate.

Use of nonrelativistic wavefunctions for the prediction of properties of molecules containing atoms of high Z. PbO as a test case

Using a minimum basis set of Slater functions, nonrelativistic self‐consistent‐field calculations have been carried out for the lead monoxide molecule. The purpose of the calculations was to provide an indirect test of the importance of relativistic effects in molecules containing atoms with atomic number as high as 82. The predicted spectroscopic constants of PbO are in about as good agreement with experiment as were the results from comparable calculations on the obviously nonrelativistic molecule CO. The electronic structures of the two molecules are briefly compared in terms of Mulliken population analyses.