Floating Gaussian basis

An interesting approach for comparison with XPS experiments is a generalization of the Floating Spherical Gaussian Orbital (FSGO) technique. In this method, each electron pair is represented by a single Gaussian basis function whose exponent and position are obtained by a variational procedure or by reference... 

Some applications of perturbation theory to molecular problems would benefit from the simplicity of an extended floating spherical Gaussian basis. Adamowicz and Bartlett ° have developed a procedure for projecting large conventional basis set wave functions onto a floating spherical Gaussian basis. 

B. Klahn, /. Chem. Phys., 83,5754 (1985). The Convergence of Cl Calculations for Atomic and Molecular Electronic Bound States in a Basis of Floating Gaussian Orbitals. 

L. Adamowicz and R. J. Bartlett, Chem. Phys. Lett., 105, 167 (1984). Extended Floating Spherical Gaussian Basis Sets for Molecules. Generation Procedure and Results for HjO. 

Furthermore, one could most probably use only two different basis sets, one for the large and one for the small component as a function of r, because the angular part of the functions is fixed in the case of an H atom. On the other hand, to maintain the possibility of basis functions not centered at the atomic nuclei (such as function centers at the midpoints of chemical bonds, or floating Gaussians), we prefer to work with four different basis sets. In a practical case the four basis sets could be equal,... 

It can be shown that the basis of spherical explicitly correlated Gaussian functions with floating centers (FSECG) form a complete set. These functions... 

Specifically, floating spherical Gaussian orbitals (FSGO), developed from an extension of Frost s simple electron pair model of molecular electronic structure, are used as basis functions in SCF-MO and Cl calculations. As will be described in the following section, these functions, unlike atomic basis orbitals, generally are not confined to atoms, but are allowed to occupy electron-rich regions corresponding... 

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