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Conformational and energetic properties of the ammonia dimer?comparison of post-Hartree?Fock and density functional methods

✍ Scribed by Kieninger, Martina; Suhai, S�ndor

Publisher
John Wiley and Sons
Year
1996
Tongue
English
Weight
1007 KB
Volume
17
Category
Article
ISSN
0192-8651

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✦ Synopsis

The equilibrium structure of the ammonia dimer has been investigated with density functional and MP2 calculations. We used Slater-and Becke-exchange functionals combined with correlation functionals as recommended by Vosko-Wilk-Nusair, by Perdew, and by Lee-Yang-Parr, respectively. The potential energy surfaces was investigated. The asymmetric cyclic "microwave" structure could be identified as a minimum. Optimization of the intermolecular parameters showed that this structure has nearly the same energy as the centrosymmetric cyclic structure. Full optimization transformed the asymmetric cyclic structure into the linear structure. The interaction energies in the dimer were corrected for the basis set superposition error using the Boys-Bernardi counterpoise method and the a priori chemical Hamiltonian approach, respectively. 0 1996 by John Wiley & Sons, Inc.

have been tested to describe the properties of small organic compounds.',2 Part of the research was dedicated to the investigation of hydrogen-bonded c ~m p l e x e s ~-~ due to their importance in biological systems. Recent studies using density functional theory (DFT) cover the region from strong to weak hydrogen bonds!-6 Among these complexes the ammonia dimer can be regarded as an especially sensitive test for the quality of ab initio calculations.

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