Carcass functions in variational calculations for few-body systems

For variational calculations of molecular and nuclear systems involving a few particles, it is proposed to use carcass basis functions that generalize exponential and Gaussian trial functions. It is shown that the matrix elements of the Hamiltonian are expressed in a closed form for a Coulomb potential, as well as for other popular particle-interaction potentials. The use of such carcass functions in two-center Coulomb problems reduces, in relation to other methods, the number of terms in a variational expansion by a few orders of magnitude at a commensurate or even higher accuracy. The efficiency of the method is illustrated by calculations of the three-particle Coulomb systems mumue, ppe, dde, and tte and the four-particle molecular systems H-2 and HeH+ of various isotopic composition. By considering the example of the (9)(Lambda) Be hypernucleus, it is shown that the proposed method can be used in calculating nuclear systems as well. (C) 2004 MAIK"Nauka/Interperiodica".