Auxiliary basis sets for density fitting second-order Møller-Plesset perturbation theory: correlation consistent...

Area of Science:

• Computational chemistry
• Quantum chemistry
• Atomic and molecular physics

Background:

• Accurate electronic structure calculations are crucial for understanding chemical properties.
• Correlated ab initio methods, such as second-order Møller-Plesset perturbation theory (MP2), are computationally demanding.
• Density fitting approximations are used to reduce the computational cost of these methods.

Purpose of the Study:

• To optimize auxiliary basis sets for density fitting in conjunction with pseudopotential-based orbital basis sets.
• To evaluate the accuracy of these new auxiliary basis sets for 5d transition metal elements (Hf-Pt).
• To assess the density fitting error in correlated ab initio calculations.

Main Methods:

• Optimization of auxiliary basis sets tailored for specific orbital basis sets (cc-pVnZ-PP, cc-pwCVnZ-PP, aug-cc-pVnZ-PP, aug-cc-pwCVnZ-PP).
• Application of density fitting approximation within second-order Møller-Plesset perturbation theory (MP2).
• Calculation of correlation energies for small to medium-sized molecules containing 5d transition metals.

Main Results:

• Auxiliary basis sets specifically matched to common correlation-consistent basis sets were developed for Hf-Pt.
• Density fitting errors using the optimized auxiliary basis sets were found to be negligible.
• The density fitting error was three to four orders of magnitude smaller than the basis set incompleteness error.

Conclusions:

• The developed auxiliary basis sets significantly improve the accuracy of density fitting for correlated calculations involving 5d transition metals.
• These optimized sets enable more reliable and efficient computational studies of molecules containing heavy transition metals.
• The negligible density fitting error validates their use in high-accuracy quantum chemical calculations.