Efficient and stable orbital-searching algorithm for the configuration interaction method and its application to quantum impurity problems
Chungwei Lin, Alexander A. Demkov
The configuration interaction (CI) method can be regarded as a generalization of the Hartree-Fock theory. The CI method includes multiple determinantal states to approximate the full many-body ground state, as opposed to just one in Hartree-Fock theory. In this work, we introduce an efficient and stable algorithm to obtain the optimal single-particle basis by formulating orbital searching in terms of a multivariable minimization problem. The algorithm is iterative and is based on imaginary-time dynamics. It is numerically efficient as the Hessian (second derivative of the energy with respect to the orbital variables) is not required; it is also stable as a reasonable initial orbital choice is not necessary. The algorithm can deal with Hamiltonians with complex coefficients. We demonstrate the power of the proposed algorithm by applying it to impurity problems, with the most complicated one including multiple correlated orbitals and spin-orbit coupling. Energies and spectral functions are computed to demonstrate the convergence of the CI method.
Physical Review B•Dec 11, 2014•5 citations