AB-INITIO INTERPRETATION OF THE CLOSED-SHELL INTERMOLECULAR E-CENTER-DOT-CENTER-DOT-CENTER-DOT-E ATTRACTION IN DIPNICOGEN (H(2)E-EH(2))(2) AND DICHALCOGEN (HE-EH)(2) HYDRIDE MODEL DIMERS

Quasirelativistic pseudopotential ab initio calculations at the second -order Moller-Plesset (MP2) level are reported on dimeric hydrides (H( 2)E-EH(2))(2) (E = As, Sb, Pi) and (HE-EH)(2) (E = Se, Te, Po), which serve as models for the nearly collinear chains found in the solid sta te for organyl-substituted molecules of this type. The intermolecular interaction is repulsive at the Hartree-Fock level but is attractive a t the MP2 level. With sufficiently large basis sets, the E E distances approach experimental ones in crystals containing (R(n)E-ER(n))infini ty chains with R = Me, SiMe(3), SnMe(3), etc. The calculated dimerizat ion energies (MP2) lie in the range from 8 to 13 kJ mol(-1), increasin g from right to left and from top to bottom in the periodic table.