Three-body exchange energies in H3 and He3 calculated by the surface integral method

Repulsive three-body exchange energies are calculated for H-3 and He-3 using a new method based on an extension of the surface integral method to three-body interactions. The dependence of the three-body exchange energies on the internuclear distances between 5 and 10 a(0) is investigated for equilateral configurations. The angular dependence is also studied for geometries in which two distances are fixed at equal distances. Very good agreement with other calculations at the same level of approximation is obtained for H-3 as well as for He-3. The relative importance of the different electron permutations in He-3 is discussed. (C) 2000 American Institute of Physics. [S0021-9606(00)30118-0].