AB INITIO STUDY OF AMMONIA CLUSTERS: (NH3)n (n = 2-6)

Herudi Kandau (Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Sekip Utara Yogyakarta 55281)
Hanggara Sudrajat (Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Sekip Utara, Yogyakarta 55281)
Andreas Napitupulu (Department of Physical Engineering, Faculty of Engineering, Universitas Gadjah Mada, Jl. Grafika No. 2 Yogyakarta 55281)
Syahrul Khairi (Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Sekip Utara, Yogyakarta 55281)
Zaky Al-Fatony (Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Sekip Utara, Yogyakarta 55281)
Herman Siagian (Physics Education Department, Faculty of Mathematics and Natural Sciences, State University of Yogyakarta, Karangmalang, Depok, Yogyakarta 55283)

Indonesian Journal of Chemistry
Vol 8, No 3 (2008)

Hydrogen bonded neutral clusters of ammonia, (NH3)n (n = 2-6), have been theoretically investigated employing the D95++(d,p) (and wherever necessary, higher) basis sets at the Hartree-Fock (HF) level as well as with second-order Møller-Plesset (MP2) perturbation theory. While the ammonia trimer and tetramer exhibit perfect molecular symmetries and are nonpolar, the pentamer and hexamer both optimize with slight deviations from perfect symmetries and are seen to posses marginal, but nonzero dipole moments. The (NH3)n linear clusters are seen to be chemically softer than the corresponding cyclic ones.