An efficient parallel algorithm for the calculation of unrestricted canonical MP2 energies

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Accurate calculation of electronic energies is crucial in chemistry.
• Open-shell systems, like radicals, present unique computational challenges.
• Second-order Møller-Plesset perturbation theory (MP2) is a widely used method for electron correlation.

Purpose of the Study:

• To present an efficient implementation of unrestricted open-shell MP2 (UMP2) energy calculations.
• To enable accurate and feasible computations for open-shell systems.
• To provide a parallelized algorithm for large-scale quantum chemistry applications.

Main Methods:

• Implementation of full accuracy unrestricted open-shell MP2 (UMP2) energies.
• Algorithm based on Saebo-Almlöf direct integral transformation.
• Serial and parallel computational approaches were developed.

Main Results:

• The UMP2 energy calculations are efficient and accurate.
• Timings for UMP2 are 1.5 to 3.0 times longer than restricted MP2 (RMP2) for similar systems.
• Demonstrated performance on large stable radicals with over 90 atoms and 3600 basis functions.

Conclusions:

• The presented algorithm offers an efficient way to compute UMP2 energies.
• This method is suitable for studying large open-shell systems.
• The parallel implementation enhances computational feasibility for complex molecular systems.