From microhydration to bulk hydration of Rb+ metal ion: DFT, MP2 and AIMD simulation study

► We report the structures and energetics of a hydrated cluster of Rb+-(H2O)n (n = 1-32) at DFT and MP2 level of theories. ► AIMD simulation was conducted to predict the CN. ► The quantum results suggest a CN of 7 for the first hydration shell of Rb+, in agreement with XAFS. ► The theoretical Rb-O bond distance is in excellent agreement with the EXAFS data. ► AIMD predicts the average first shell CN of 6.31 at both PW91 and PBE levels of theories.