Structure and energetics of H-15(+) hydrogen clusters

Low-lying stationary points on the H-15(+) potential energy hypersurface ha ve been determined through Hartree-Fock (HF) calculations and density funct ional theory (DFT) with the recently proposed functional especially designe d for hydrogen systems [B3(H)]. Calculations have been carried out for thre e conformers of H-15(+) (C3v, Cs, and D3h symmetries) leading to fully opti mized structures and energies. Only the C3v and Cs structures are true mini ma. The total energy of the Cs structure lies 10(-4) Hartrees lower than th e C3v one. Vibrational frequencies and infrared intensities for both statio nnary points have been predicted within HF and DFT B3(H) methods. [S0163-18 29(99)12029-0].