Acceleration of Self-Consistent Field Calculations Using Basis Set Projection and Many-Body Expansion as Initial...

Area of Science:

• Computational chemistry
• Quantum chemistry
• Theoretical chemistry

Background:

• Self-Consistent Field (SCF) calculations are fundamental in quantum chemistry.
• The initial guess significantly impacts SCF convergence speed and computational cost.
• Traditional superposition of atomic densities (SAD) may not be optimal for all systems.

Purpose of the Study:

• To evaluate the efficiency of basis set projection (BSP) and many-body expansion (MBE) for SCF initial guesses.
• To introduce and assess a hybrid MBE-BSP initial guess method.
• To compare these methods against SAD for Hartree-Fock (HF) and DFT (B3LYP, MN15) calculations.

Main Methods:

• Implementation and testing of BSP, MBE, and a hybrid MBE-BSP initial guess approach.
• Assessment of computational time, including initial guess generation and SCF iterations.
• Application to systems up to 14,386 basis functions, including challenging metalloprotein and triplet states.

Main Results:

• BSP, MBE, and hybrid methods show significant improvements over SAD.
• Total wall-time reductions of up to 27.6% were achieved across HF, B3LYP, and MN15.
• Speedups were observed for difficult systems, though triplet states showed increased convergence failures.

Conclusions:

• Advanced initial guess strategies like BSP and MBE offer substantial computational savings in SCF calculations.
• The hybrid MBE-BSP method provides a competitive alternative.
• Careful consideration of initial guess methods is crucial for optimizing quantum chemical computations, especially for complex systems.