Structure and vibrational spectra of neutral, protonated and deprotonated hydrogen bonded polymers: an ab initio SCF study on chain-like hydrogen fluoride clusters

Abstract

The total energies, the structures, the HF bond stretching frequencies and the corresponding IR intensities of neutral ((HF) n ) protonated ([(HF) n H] +) and deprotonated ([(HF) n−1 F] −) chain-like hydrogen fluoride polymers were investigated at the ab initio SCF level by applying a double-zeta type basis set. Clusters from n = 1 up to n = 19 were treated. We adopted a systematic approach and minutely monitored these properties as a function of cluster size. Particular emphasis was laid on the various aspects of non-additive behaviour in these series, visible in the substantial structural relaxations of HF and FF distances, in the increased stabilization energy per hydrogen bond, in the strong red-shifts of HF bond stretching frequencies, and in significantly enhanced IR intensities. We investigated in detail the convergence of this selected number of ground-state properties with increasing chain length and we discuss the different mode of convergence encountered in the neutral chains and in the chains carrying a charged defect.