Chemical Physics Letters vol:334 issue:4-6 pages:325-329
The correlation factor in the explicitly correlated wave function for the ground state of the helium atom has been analyzed. The general structure of the correlation factor (including its angular dependency) in the region of small viz has been obtained. The 'extent of non-sphericity' of the correlation factor, g(r(1), r(2), r(12)), is proportional to the first derivative of logarithm of the 'coalescence function' h(r) = g(r, r, 0). (C) 2001 Elsevier Science B.V. All rights reserved.