Gaussian lobes

Contracted gaussian lobes (i.e. combinations of only simple gaussians) are frequently used as basis functions (21). For large molecules the lobes may be... 

A minimal basis set of STO (expanded in Gaussian lobe functions) was used, and the least-energy pathway determined, assuming fixed values for some of the parameters. The complete optimization is not practicable for systems of this size and most surface studies make physically reasonable approximations to reduce the number of variables. The computed pathway is a non-least-motion rearrangement. The implications of the results with respect to the stability of F2NOF relative to F3NO were also discussed. 

A related set of calculations by Hart115 also studied NH30 and its stability with respect to NELOH. Gaussian lobe basis functions with a similar quality basis set to that in earlier work were used.116... 

Ha and co-workers158 carried out Gaussian lobe SCF calculations of approximately DZ quality. Several conformations were considered and the three-membered ring was found to be the most stable, with the CH2 and C02 groups perpendicular to one another. 

Table 4. CEPA calculation32) of planar NH3 with 172 Gaussian lobes in 58 groups on a UN1VAC 1108...

Constants for Gaussian Lobe and Gaussian-Type Wave Functions. 

The original VB method has been difficult to use in practice because of the nonorthogonality of the atomic orbital basis, but there has been a revival of interest in it recently. Gallup and co-workers116-118 have described a new technique for carrying out such calculations, and the results of applications to the first-row hydrides. Calculations were carried out using a minimal basis set constructed from gaussian lobe orbitals. The orbitals were scaled to their best atom value and also optimally scaled in the molecule. Atomic populations were also computed.118... 

A. He/H2 and Ha.—It is convenient to consider first these species. Tsapline and Kutzelnigg375 have applied the IEPA-PNO method, previously described, to the ground state of the He/Ha system. The van der Waals minimum was computed, using a gaussian lobe basis set with carefully optimized exponents. The collinear arrangement with a depth of 21 K was found for the van der Waals minimum, with a saddle point of 14 K for the Czv geometry. The computed surface was compared with experiment and with the R 6 term. The anisotropy of the potential is larger than that predicted asymptotically. 

There have also been a few VB calculations. An early calculation by Harrison and Allen used a small gaussian lobe basis set,446 and included 20 primary structures. The resulting lowest energy of —38.915 hartree and bond angle of 140° were similar to the values obtained by MO calculations.447... 

The Gaussian lobe function method was introduced by Preuss and developed for routine calculations by Whitten. The contraction of Gaussian lobe function (GLF) basis sets is made along the same lines as with Cartesian GTF s. As regards the primitives, the s-type functions are expressed in the usual way. But the primitives of p, d, f,. .. types are expressed as linear combinations of s-Gaussians (lobe functions) placed at different points so as to retain the proper symmetry (see Fig. 2,4 ). Thus, a p-type function on nucleus A may be... 

CEPA calculations of planar NH with 172 Gaussian lobes 58 groups on a UNIVAC 1108... 

Meier and Vogelsangi" described the adaptation of an existing serial Gaussian lobe SCF program to the SUPRENUM system. They described the basic features of the hardware, programming environment, and the user interface. 

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