Precise Quantum Chemistry calculations with few Slater Determinants.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Slater determinants are fundamental in quantum chemistry but challenging to fully utilize.
• Accurate electronic structure calculations are crucial for understanding molecular properties.

Purpose of the Study:

• To develop and validate a novel variational wavefunction method using optimized non-orthogonal Slater determinants.
• To achieve high energy accuracy comparable to or exceeding state-of-the-art methods.

Main Methods:

• Employing a variational wavefunction composed of hundreds of optimized non-orthogonal determinants.
• Utilizing an iterative optimization method exploiting the quadratic energy dependence on determinant orbitals.
• Implementing an efficient tensor-contraction algorithm for effective Hamiltonian evaluation with O(N^4) scaling.

Main Results:

• The proposed method achieves energy accuracies comparable to state-of-the-art quantum chemistry techniques.
• Demonstrated lower variational energies than coupled cluster (CCSD(T)) for several molecules in double-zeta basis.
• Method validated against exact full-configuration interaction results where available.

Conclusions:

• Optimized non-orthogonal Slater determinants offer a powerful approach for accurate quantum chemical calculations.
• The developed method provides a computationally efficient and accurate alternative to existing high-level electronic structure methods.
• This work unlocks the potential of Slater determinants for advanced computational chemistry applications.