Electronic density
fitting Using Elementary Jacobi Rotations under Atomic Shell Approximation
(ASA)
ASA density functions have permitted to extend quantum similarity measures to real problems in pharmacological drug design. This approximation expresses electron density functions as a linear combination of spherical functions. The main attribute of ASA electron density consists in the fact that expansion coefficients are maintained positive definite, preserving the statistical meaning of density function into the fitted structure. An algorithm based on elementary Jacobi rotations (EJR) technique is an efficient electron density fitting procedure. The capabilities of the EJR technique justify its use in electron density fitting, both for atoms and molecules.
The ASA density
function is constructed using the following formula:
where {j i} is the
normalized 1S-type GTO basis set, and {wi}
represents the ASA coefficients submitted to the convex constraints:
together provide a
normalized description of ASA electron density:
Some examples of
atomic ASA density functions can be found in:
- 1S-type Gaussian basis for atoms H to Kr
fitted from a 3-21G basis set.
- 1S-type Gaussian basis for atoms H to Ar
fitted from a 6-311G basis set.
- 1S-type
Gaussian basis for atoms H to Rn fitted from a Huzinaga basis set.
Last updated: 17 March 2000, by Lluís Amat