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Abstract: The nuclear quantum effect, which plays important roles on ionic hydrogen bonded structures of Cl−(H2O) n (n =1–4) clusters, was explored by carrying out path integral molecular dynamic simulations. An outer shell coordinate rl (Cl⋯O) is selected to display the rearrangement of single and multi hydration shell cluster structures. By incorporating the nuclear quantum effect, it is shown that the probability for single shell structures is decreased while the probability for multi shell structures is increased. On the other hand, the correlations between changing of bonded H∗ atom to Cl− (defined as δ) and other cluster vibration coordinates are studied. We have found that δ strongly correlates with proton transfer motion while it has little correlation with ion–water stretching motion. Contrary to θ(H–O–H∗) coordinate, the correlations between δ and other coordinates are decreased by inclusion of nuclear quantum effect. The results indicate that the water–water hydrogen bond interactions are encouraged by quantum simulations. [Copyright &y& Elsevier]

Abstract: The interaction energies and hydrogen bond structures of water–ammonia mixed trimer clusters, (H2O) n −3(NH3) n (n =0,1,2,3), were analyzed by means of a multi-component molecular orbital method, which directly accounts the quantum effects of protons. We found that the protonic quantum effects directly influenced the flexible description of geometrical parameters and electronic populations. Deuterated water and ammonia were used to estimate the intermolecular interaction energies and hydrogen bond structures. The interaction energies of deuterated complexes were smaller than those of protonated ones, because the hydrogen bond distances in the deuterated complexes were longer than those in their protonated analogs. We also analyzed the stability afforded by formation of cyclic trimer structures and induced by the hydrogen/deuterium isotope effect. Through the replacement of protons with deuterons, the difference in quantum effects between protons and deuterons was reflected in the interaction energies and hydrogen bond structures. [Copyright &y& Elsevier]

To elucidate site-specific phenomena, we experimentally and computationally studied the spectroscopy and dynamics caused by Si:2p core-level photoexcitation of bridged trihalosilyl–trimethylsilyl molecules. We used the photoionization efficiency curve and the photoelectron photoion coincidence method to study the site-specific phenomena in the Si:2p photoexcitation of F3SiCH2CH2CH2Si(CH3)3, F3SiCH&z.dbnd6;CHSi(CH3)3 and Cl3SiC&z.tbnd6;CSi(CH3)3 in the vapor phase. The site-specific excitation was revealed in the photoionization efficiency curves of all the molecules. The site-specific fragmentation is likely to be more evident when the distance between the two Si sites is large. For the site-specific fragmentation to be caused by the Si:2p photoexcitation, there should not be a C&z.tbnd6;C bond between the atomic site of interest and any other near atomic site around which bond dissociation is undesirable. Not only initial-state effect but also final-state effect is likely to contribute to the occurrence of the different chemical shifts between the two Si sites of the bridged trihalosilyl–trimethylsilyl molecules. [Copyright &y& Elsevier]