DFTB-based QM/MD simulations of nanostructure formation processes far from
thermodynamic equilibrium

Stephan Irle, stephan@euch4e.chem.emory.edu1, Zhi Wang, zwang6@emory.edu2,
Guishan Zheng, gzheng@emory.edu2, and Keiji Morokuma, morokuma@emory.edu2. (1)
Fukui Institute for Fundamental Chemistry, Kyoto University, Takano
Nishihiraki-cho 34-4, Sakyo-ku, Kyoto, 606-8103, Japan, (2) Cherry L. Emerson
Center for Scientific Computation and Department of Chemistry, Emory University,
1515 Dickey Drive, Atlanta, GA 30322

The maintenance of organization in nature is not -- and cannot be -- achieved by
central management; order can only be maintained by self-organization [1]. With
this realization at the end of the last century we have come to recognize that
fundamental understanding of nanostructure formation processes requires modeling
of dissipative systems open to energy and interaction with environment. The
study of reaction pathways such as A + B --> C associated with isolated reaction
systems in a traditional quantum chemical modeling sense is inherently flawed by
the failure to describe the emergent features of systems far from thermodynamic
equilibrium exhibiting self-assembly and auto-catalytic processes, which are
omni-present in the biological as well as carbon nanotechnological world. We
present successful applications of the DFTB method as basis for quantum chemical
molecular dynamics (QM/MD) simulations of fullerene and metallofullerene
formation (see Figure 1) and synthesis of carbon nanotubes from SiC and from
carbon-containing feedstock gases in the presence of metal catalysts, using
parameters developed in our group. The application of DFTB as high or
intermediate level in ONIOM-based MD simulations for the modeling of
nanostructures far from thermodynamic equilibrium will also be addressed in this
talk.


[1] C. K. Briebacher, G. Nicolis, and P. Schuster, Self-Organization in the
Physico-Chemical and Life Sciences, Report EUR 16546 (European Commission, 1995)