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An explicitly correlated second order Møller-Plesset theory using a frozen Gaussian geminal
Andrew J May1, Frederick R Manby
1School of Chemistry, University of Bristol, Cantocks Close, Bristol BS8 1TS, United Kingdom.
The Journal of Chemical Physics
|August 31, 2004
Summary
This study introduces a new MP2-R12 theory variant using Gaussian geminals for improved electron correlation calculations. This method simplifies integral calculations, enabling more efficient and accurate quantum chemistry computations.
Area of Science:
- Quantum Chemistry
- Computational Physics
- Theoretical Chemistry
Background:
- Explicitly correlated methods, such as MP2-R12, are crucial for accurately describing electron correlation.
- Standard methods often struggle with the slow convergence of correlation energy with basis set size.
- The interelectronic distance (r12) term presents computational challenges.
Purpose of the Study:
- To introduce a novel variant of the MP2-R12 theory.
- To develop an efficient computational approach for explicitly correlated calculations.
- To assess the performance of the new method on small atomic and molecular systems.
Main Methods:
- A modified MP2-R12 theory employing an arbitrary geminal function instead of r12.
- Derivation of integrals for Gaussian-expanded geminal functions.
- Development of recurrence relations independent of Gaussian geminal exponents.
- Summations over the geminal expansion performed after integration.
Main Results:
- Successfully derived necessary integrals and recurrence relations for the new theory.
- Demonstrated that integration can be significantly simplified by performing it after geminal expansion summations.
- Presented sample calculations using various levels of explicitly correlated MP2 theory.
Conclusions:
- The proposed MP2-R12 variant offers a computationally tractable approach to electron correlation.
- The method shows promise for accurate and efficient quantum chemical calculations.
- Further applications to larger systems are warranted to fully explore its potential.