AN INTERACTION POTENTIAL BETWEEN AN VALINE ZWITTERION AND A WATER MOLECELE BASED ON AB INTTIO CALCULATIONS
基于从头算的缬氨酸两性离子和水分子的相互作用势

Interaction energies between a valine zwitterion and a water molecule at 160 different positions and orientations have been calculated by ab initio method with the minimal basis set and by the counterpoise method to eliminate the basis set superposition error . Dispersion energies were estimated by using the Slater - Kirkwood formula . Out of a total 160 computed interaction energies , 148 whose SCF interaction energies were below 5 Kcal/mole have been fitted with a summation of atom-atom pair potentials in the form of the Lennard - Jones potential plus an electrostatic term ( -Aij/rij6 + Bij/fij12 + 332.06CijQiQj/rij). During the fitting , we used a new scheme to keep A>0 and B>A . The standard deviation for this fitting is 0.48 Kcal/mole.