Dresden 2003 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

SYCN: Computational nanoscience - from materials to biology

SYCN 102: Computational Nanoscience: From Materials to Biology (Poster, gemeinsam mit SYSE)

SYCN 102.5: Poster

Dienstag, 25. März 2003, 19:00–21:00, ZEU/160

Ab initio molecular dynamics simulations of liquid and supercritical ammonia — •Amalendu Chandra and Dominik Marx — Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

The structure and dynamics of ammonia under ambient and supercritical conditions are investigated by means of Car-Parrinello molecular dynamics [1]. The results are obtained for two different density functionals: BLYP [2,3] and the HCTH/407+ [4]. The latter functional is designed to reproduce the experimentally observed bent hydrogen bonded structure of the ammonia dimer for which the BLYP functional gives an essentially linear hydrogen bond. For the liquid ammonia, however, it is found that the bent character of the hydrogen bonds is reduced due to many-body effects. The hydrogen bonds are found to persist even in the supercritical phase of ammonia studied here. The atom-atom radial distribution functions, diffusion coefficients and the orientational relaxation times of the ammonia molecules are also calculated and are compared with experimental results wherever available.

[1] R. Car and M. Parrinello, Phys. Rev. Lett. 55, 2471 (1985).

[2] A.D. Becke, Phys. Rev. A 38, 3098 (1988); J. Chem. Phys. 96, 2155 (1992).

[3] C. Lee, W. Yang and R.G. Parr, Phys. Rev. B 37, 785 (1988).

[4] A.D. Boese, J.M.L. Martin, A. Chandra, D. Marx and N.C. Handy, to be published.