Kinetic energy matrices in a basis of equidensity orbitals

Abstract

The matrix of the kinetic energy operator can be divided into two components, one of which is equivalent to the matrix of a function so that it is effectively local. This decomposition is basis-set dependent and is particularly simple when equidensity orbitals are used. It is shown that for a one-dimensional problem the norm of the local component is √5/3 times the norm of the whole kinetic energy matrix, independent of the density used to define the orbitals. In the three-dimensional case this ratio depends on the density but reasonably simple expressions are obtained.