Albert K. Q. Siu

Nonempirical LCAO MO SCF studies of the group IIa dihalides BeF2, MgF2, and CaF2

Nonempirical LCAO MO SCF calculations are reported for the ground, C2ν states of the Group IIa dihalides, BeF2, MgF2, and CaF2. These calculations demonstrate the importance of 3d orbitals in the bonding trends of the dihalides and, hence, in the determination of the equilibrium bond angles and the bending force constants. The calculations on BeF2 indicate that d orbitals play an important role in the bonding but do not preferentially alter the general features of the total energy curve at any bond angle. In the case of MgF2, d orbitals are found to preferentially lower the energy of the nonlinear configurations. However, for both species, the ground‐state equilibrium bond angle is predicted to be 180°. Configuration interaction studies also support the fact that, in the gas phase, the linear configuration is most stable. On the basis of s(1s, 2s, 3s, 4s, 2p, and 3p orbitals on Ca) basis set calculations, it is predicted that CaF2 is linear. However, when 3d orbitals are added to the s basis set, the pred...

Potential surface for the collinear collision of Ne and H2

A potential energy surface for the Ne–H2+ reaction has been obtained in the LCAO–MO–SCF approximation. Analysis of the surface indicates that the reaction Ne+H2+→NeH++H should proceed with an endoergicity of 12 kcal/mole, in agreement with the experimental results of Chupka and Russell. Several procedures for parameterizing a diatomics‐in‐molecules (DIM) representation of the NeH2+ surface are considered. The results show that an accurate representation of the SCF surface can be obtained from the DIM model using a minimum of diatomic and triatomic data.

Non-empirical SCF studies of the ring and open forms of ozone☆

Abstract Non-empirical SCF calculations have been used to investigate the relative stabilities of the open and closed forms of ozone. In these studies several different sized basis sets have been employed, the best basis set being at about the level of a double-zeta set plus d-polarization functions. In contrast to the predictions of the CNDO/2, INDO and MINDO methods, the non-empirical SCF studies correctly predict that the open form of ozone is more stable. Thus these results show that the area of deficiency in the CNDO/2, INDO and MINDO results for this system is not in the SCF approximation.

Configuration interaction procedure based on the calculation of perturbation theory natural orbitals: Applications to H2 and LiH

A configuration interaction method, based on the calculation of perturbation theory natural orbitals, is presented. The method offers an attractive alternative to commonly used procedures for obtaining truncated configuration interaction wavefunctions. Studies of H2 and LiH indicate that natural orbitals obtained using first order perturbation theory are nearly identical to those obtained by standard configuration interaction techniques.

Electronic structure of the open forms of three-membered rings

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Theoretical studies of the low-lying electronic states of the nitrenium ion (NH+2 and methylene

A. Buchler, J. L. Stauffer and W. Klemperer, J. Amer. Chem. Soc. 86, 4544 (1964).

Theoretical studies of trimethylene

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THEORETICAL STUDIES OF THE INTERACTION OF

D. E. Mann, G. V. Calder, K. S. Seshadri, D. White and M. J. Linevsky, J. Chem. Phys. 46, 1138 (1967).