Project: Research project

Project Details


The recently developed DMoI/COSMO model for calculation of the
electronic and geometrical structure of molecules in solution has been
further tested ana optimized for the parallel system CRAY T3D at SDSC.
In the DMoI/COSMO model, the solute molecule is embedded into a cavitv
surrounded by solvent, which is represented by a dielectric continuum.
The polarization of the dielectric continuum by the charge
distribution of the solute results in a charge distribution on the
cavity surface. In the COSMO method, the surface charges are obtained
directly from the electrostatic potential on the cavity surface. This
represents the major computational advantage. Since the 'DMoI/COSMO
energy is fully variational, accurate gradients with respect to the
solute coordinates can be calculated.
The DMoI/COSMO theory and applications have been presented 1] and
published [2]. DMol1COSMO became a part of our software offering
within the DMoI 3.0.0 release. This indicates that the program was
thoroughly debugged and strict quality assurance protocols were
followed. Further validation of the method was performed, in
particular optimization of the van der Waals radii and the computation
of the non-electrostatic contributions. The COSMO procedure was
optimized to some degree as well by, e.g. employing a more efficient
linear equation solver.
The DMoI/COSMO program was optimized for the CRAY T3D platform [3]
and it is avail-able at SDSC for academic NIH users, according to the
terms of the NIH grant. A distributed memory model is used for
running DMoI on concurrent processors. Communication between
processors occurs via messages, using the Message Passing Interface
There are two distinct phases of computation in DMol program. In
short, there is a domain of the program which depends on the molecular
numerical integration grid and another domaln which is governed by the
orbital basis set. The first domain involves setup of the integration
grid, numerical integration and density synthesis, whereas the orbital
part involves various matrix operations and diagonalization of the
Hamiltonian matrix.
At present the grid dependent part of DMol is fully parallelized
whereas diagonalization is still done in single processor mode. The
performance of DMol was tested for the zeolite model cluster
Si8O25Hl8. The grid-dependent part of the calculations scales
linearly with the number of CRAY T3D processors (up to 64), whereas
diagonalization (non parallel) takes about 3% of the total wall clock
time for a single processor run. We are currently incorporating a
parallel diagonalization routine in DMol.
[l] ACS meeting, Anaheim, 1995, 6th International Conference
on the Application of the DFT in Chemistry and Physics,
France, 1995
[2] J. Andzeim, Ch. Koelmel, A. KIamt, J. Chem. Phys. 103
(1995) 9312-9320.
[3] Y.S. Li, M.C. Wrinn, J.M. Newsam, M.P. Sears, J. Comp.
Chem. 16 (1995) 226. H. Pritchard, E. Bierwagen, Y.S. Li,
Andzelm, to be published
[4] Message Passing Interface Forum. 'Document for a Standard
Message-Passing Interface",
Technical Report No. CS-93-214 (revised), University of
April 1994.
StatusNot started


  • National Center for Research Resources
  • National Center for Research Resources


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