| Explicitly
Correlated Methods for Computations of Properties to Chemical
Accuracy
The goal of this project is to develop efficient methods for
incorporating dynamical electron correlation effects into molecular
quantum mechanics by using basis sets that depend explicitly
on the interelectronic distance (R12). This will allow extremely
high accuracy in calculating the electronic structure of atoms,
molecules, and clusters (Figure 6) while dramatically reducing
the number of basis functions needed to describe the electron-electron
correlation cusp, thus dramatically reducing the computational
costs.
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| Figure
6 Achieving the full promise of molecular
quantum mechanics through next-generation, explicitly
correlated electronic structure methods. |
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The first application of the MP2-R12/A code was published
in a study of the second-order Møller-Plesset limit
for the barrier to linearity of water. Here, the basis set
limit to the barrier of linearity of water was computed and
found to match well with the most recent empirical value.
The authors found that basis functions with orbital quantum
number higher than 3 (i.e., g and higher) are essential for
spectroscopic accuracy. This finding differs from previous
claims that computations saturated only to the f
level were all that is necessary for spectroscopic accuracy
with explicitly correlated approaches. Ongoing research seeks
to approach the basis set limit via plane wave expansions
(that is, basis sets are constructed so as to saturate each
angular momentum level sequentially) in order to explore more
fully the contribution of each level.
INVESTIGATORS
H. F. Schaefer III, W. D. Allen, J. Kenny, N. Richardson,
K. Sattelmeyer, and M. Schuurman, University of Georgia.
PUBLICATION
E. F. Valeev, W. D. Allen, H. F. Schaefer III, and A. G. Császár,
“The second-order Møller-Plesset limit for the
barrier to linearity of water,” J. Chem. Phys. 114,
2875 (2001).
URL
http://zopyros.ccqc.uga.edu/scidac/scidac-intro.html |
