The intermolecular geometry of the weak hydrogen-bonded complex PH~3. ..H~2O was optimized using the second-order Moller-Plesset perturbation theory (MP2) at 6-311++G (3d, 3p) level. Three equilibrium structures (A, B and C) was found. The geometry A, which exhibits the conventional structural features of a hydrogen-bonded system with H~2O as the proton donor, is the most stable one in the three equilibrium structures. Using the geometry A, which has C~s symmetry and R(P...O)=354.78nm, correlation energy has been calculated with 6-311++G(3df, 3pd) basis set adding bond function {3s3p2d1f} using MP2, and MP4SDTQ. The computed binding energy is -10. 84kJ/mol at MP4SDTQ level.

Key words: AB INITIO CALCULATION, HYDROGEN BONDS, INTERACTIONS, PHOSPHOROUS HYDRIDE, WATER