Second order Møller-Plesset perturbation theory based upon the fragment molecular orbital method

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Accurate electronic structure calculations are crucial for understanding molecular properties.
• Traditional methods like MP2 struggle with computational scaling for large systems.
• Fragment-based methods offer a potential solution to computational limitations.

Purpose of the Study:

• To develop and validate a Fragment Molecular Orbital (FMO) method combined with second-order Møller-Plesset (MP2) perturbation theory (FMO2-MP2).
• To assess the accuracy of FMO2-MP2 for calculating correlation energy, gradients, and dipole moments.
• To evaluate the computational efficiency, scaling, and memory requirements of FMO2-MP2 compared to standard MP2.

Main Methods:

• Combining the Fragment Molecular Orbital (FMO) method with second-order Møller-Plesset (MP2) perturbation theory.
• Testing the FMO2-MP2 method with 6-31G(*) and 6-31++G(**) basis sets on water clusters and alanine peptides.
• Introducing and testing an approximation for reduced computational load based on fragment separation.

Main Results:

• FMO2-MP2 demonstrated high accuracy, with errors in correlation energy, gradient, and dipole moment comparable to regular MP2.
• The method exhibited nearly linear scaling with system size.
• Significant reductions in memory requirements were observed, enabling calculations on large systems with limited resources.

Conclusions:

• The FMO2-MP2 method provides an accurate and computationally efficient alternative to standard MP2 for large molecular systems.
• This method drastically reduces computational cost and memory usage, making complex calculations feasible on standard hardware.
• FMO2-MP2 opens possibilities for studying larger and more complex molecular systems previously intractable with traditional methods.