Dear all,
I am using Gaussian to investigate the binding energy of CH3CH2Se- and imidazolium in water, what puzzles me is that the result is positive. Isn't it should be negative for the ion pair which carry opposite charges. The calculation process and methods are as follows:
1. Geometries Optimization for ion pair, anion and cation: B3LYP-D3/6-31+G**,scrf ,net charge and spin multiplicity are 0,1;-1,1;1,1 respectively.
2. Single point eennergy calculation for ion pair, anion and cation: M062X-D3/ma-def2-TZVP, scrf=smd
3. Binding energy calculation accordding to Ebind= Eion pair -Ecation-Eanion