Variational procedure for nuclear shell-model calculations and energy-variance extrapolation

TL;DR

This paper introduces a variational approach for nuclear shell-model calculations and improves energy-variance extrapolation by reordering wave function components to address estimation difficulties.

Contribution

It proposes a new reordering procedure for Slater determinants that enhances the accuracy of energy-variance extrapolation in shell-model calculations.

Findings

Reordering Slater determinants improves EVE accuracy.

Shape coexistence affects EVE estimation.

Method reduces uncertainty in energy extrapolation.

Abstract

We discuss a variational calculation for nuclear shell-model calculations and propose a new procedure for the energy-variance extrapolation (EVE) method using a sequence of the approximated wave functions obtained by the variational calculation. The wave functions are described as linear combinations of the parity, angular-momentum projected Slater determinants, the energy of which is minimized by the conjugate gradient method obeying the variational principle. The EVE generally works well using the wave functions, but we found some difficult cases where the EVE gives a poor estimation. We discuss the origin of the poor estimation concerning shape coexistence. We found that the appropriate reordering of the Slater determinants allows us to overcome this difficulty and to reduce the uncertainty of the extrapolation.