A NUMERICAL STUDY OF THE FUNCTIONAL DERIVATIVE OF THE KINETIC PART OFTHE DENSITY-FUNCTIONAL CORRELATION-ENERGY

Accurate functional derivatives of the kinetic part of the density fun ctional correlation energy for two-electron systems are calculated num erically from the adiabatic coupling constant relation delta T-c(gamma )[rho]/delta rho(r) = upsilon(c)(gamma)([rho];r)-gamma partial derivat ive/partial derivative gamma-upsilon(c)(gamma)([rho];r). The kinetic e nergy potential delta T-c(gamma)[rho]/delta rho(r) resembles a scaled mirror image of the correlation potential upsilon(c)(gamma)([rho];r). Numerical results show that the correlation energy functional and the kinetic part of the correlation functional are not homogeneous of any degree in density scaling. It may still be possible to express the cor relation energy as a combination of homogeneous functionals of differe nt degrees as suggested by Lui and Parr. (C) 1998 Elsevier Science B.V . All rights reserved.