Proton Motion and Proton Transfer in the Formic Acid Dimer and in 5,8-Dihydroxy-1,4-naphthoquinone: A PAW Molecular Dynamics Study

摘要: A molecular dynamics study on proton motion and (double) transfer in the formic acid dimer (FAD) 5,8-dihydroxy-1.4-naphthoquinone (DHN) is reported that has been performed with Projector Augmented Wave method (PAW). PAW trajectories were calculated a time interval of 0.12fs, for evolution periods up to 20ps, temperatures range 500–700 K. Two basic situations can be clearly distinguished: normal correspond asymmetric O-H ¨O hydrogen bonds, where remains trapped at one oxygen atom, active (near-)symmetric O ¨ H undergoes large amplitude motions between two adjacent atoms. Within may distinguish isolated transitions, just moves from other crossing-recrossing events, atom but almost immediately turns back, shuttling periods, several consecutive transitions. Moreover, also single processes, only group involved, double both groups are simultaneously involved. It shown reasonable descriptive understanding processes obtained by considering potential energy governs main difference FAD DHN concerns processes. In first case these exclusively simultaneous one-step whereas second mainly two-step i.e. successive This attributed fact process yields metastable 4,8-dihydroxy-l,5-naphthoquinone tautomer, does not result intermediate.