The unbiased diffusion Monte Carlo: a versatile tool for two-electron systems confined in different geometriesGaia Micca Longo, Carla Maria Coppola, Domenico Giordano and Savino LongoEur. Phys. J. D, 75 3 (2021) 83DOI: https://doi.org/10.1140/epjd/s10053-021-00095-7