Quaternion Dynamics
for Dynamical Simulations
in Computational Nanotechnology
Oak Ridge National Laboratory
This is an abstract for
a poster to be presented at the
Fifth
Foresight Conference on Molecular Nanotechnology.
There will be a link from here to the full article when it is
available on the web.
While previous computational models of nano-systems have
almost exclusively employed fully atomistic classical molecular
dynamics simulations, by analogy to macroscopic systems, it can
be intuited that the dynamical performance of nano-machines will
be governed predominantly by the gross movements of their
components and not by the details of the motion of the individual
atoms. This observation suggests that accurate predictions about
the performance of nano-systems can be achieved through the use
of the rigid body approximation. Furthermore, fully atomistic
classical molecular dynamics simulations can exhibit excessive
vibrational motion which results from pooling of the quantum
zero-point vibrational energy into low frequency modes, a process
not quantum mechanically allowed. The rigid body approximation
evades the zero point energy problem.
One complication which arises with the use of the rigid body
approximation is that the orientation of each body must be
specified as well as its position. The conventional Euler angles
for specifying orientation are inappropriate for use in numerical
simulations because they become singular for certain orientations
of the body. An elegant solution to this problem is found in the
use of quaternion parameters. We will discuss the use of the
quaternion parameters in nanotechnology simulations and present
example applications.
Related work: gopher.CCS.ORNL.GOV/vizlab/animations.html
*Corresponding Address:
Karl Sohlberg, Oak Ridge National Laboratory, Chemical
and Analytical Sciences Division, 4500N MS6197, Oak Ridge, TN
37831-6197, ph: 423-576-4974, fax: 423-576-5235, email: [email protected]
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