A general non-Abelian density matrix renormalization group algorithm with application to the C2 dimer.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Previous work established a spin-adapted density matrix renormalization group algorithm.
• General non-Abelian point group symmetries were not fully integrated into such algorithms.

Purpose of the Study:

• To extend the spin-adapted density matrix renormalization group algorithm to incorporate general non-Abelian point group symmetries.
• To develop a versatile implementation capable of enabling or disabling various symmetry groups dynamically.

Main Methods:

• The study employed a novel formulation for tensor operators, generated dynamically using Clebsch-Gordan coefficients.
• The algorithm was applied to compute the ground state potential energy curve of the C2 dimer using the cc-pVQZ basis set.
• Calculations included determining excitation energies for eight low-lying states and potential energy curves for twelve states.

Main Results:

• The computed ground state energy for the C2 dimer achieved a high accuracy (0.01 mEh residual error), surpassing previous methods.
• Excitation energies for eight states agreed with experimental values to within 0.06 eV.
• Potential energy curves for twelve states were calculated with an estimated accuracy of 0.1 mEh.

Conclusions:

• The developed method efficiently handles complex symmetry groups in electronic structure calculations.
• The enhanced algorithm provides highly accurate energy and excitation data for molecular systems.
• This work offers a significant advancement in computational quantum chemistry for studying molecular properties.