A comparative study of structure and electrostatic potential of hydrogen-bonded clusters of neutral ammonia,(NH3) n (n= 2–6)

Abstract

A comparative study is introduced to assess the performance of the hybrid density functionals B3P86, B3LYP, B3PW91 and B1LYP, as tools for studying the hydrogen-bonded clusters of neutral ammonia (NH3)n (n=2–6) with a 6-31++G(d,p) basis set. The electrostatic potentials V(r) on cluster surfaces were mapped using the generated wavefunctions of the optimized clusters. The physical significance of the potential minima and maxima VS,min(r), VS,max(r) is investigated in terms of their sites and the directionality of the cluster hydrogen-bonding. The functionals B3LYP and B3P86 showed high relative stabilities and excellent structural and/or electronic trends in agreement with Hartree–Fock and Møller–Plesset approaches. The computed energies of the frontier orbitals and their subsequent gaps vary rather little for each of the functionals so that the trends in εHOMO and εHOMO–LUMO might be physically …