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Short Report


ScienceAsia 15 (1989): 203-213 |doi: 10.2306/scienceasia1513-1874.1989.15.203

 

THE INTERMOLECULAR POTENTIAL FUNCTION FOR AMMONIA-MAGNESIUM ION BASED ON AB-INITIO CALCULATIONS

 

SUPOT V. HANNONGBUAa, SUCHADA KHEAWSRIKULb AND MICHAEL M. PROBSTc

ABSTRACT: An intermolecular potential function for ammonia-magnesium ion (NH3/Mg(II)) has been derived based on the data from ab-initio molecular orbital calculations with a minimal Oausian Lobe (OLO) basis set. The 120 interaction energies, E, between two monomers were fitted to an analytical potential of the form

E(kcal.mol-1) = 4i=1 [-Aim.exp(-Bimrim] - Cim/r6im + Dim/r4im + Fqiqm/rim] where 4 is number of atoms in ammonia, Aim, Bim, Cim, Dim and F are constants and rim is distance between the ith atom of ammonia and magnesium ion. qi and qm are atomic charges of ammonia and magnesium ion, respectively. The resulting function is tested by searching for unwanted minima. In comparison with other ions in an identical solvent, based on a more extended basis set, Monte Carlo simulations using this function have led to encouraging results.

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Engler-Bunte Institute, University of Karlsruhe, 7500 Karlsruhe, Federal Republic of Germany.

Received 12 April 1989