“…Gimarc [20] used the same method but employing 5 different trial wave functions, one of which produced results similar to the HF calculations, and two of them explicitly included electronic correlation. Subsequent to Gimarc, different methods have been developed, for example, Hartree-Fock [21], Roothaan-Hartree-Fock [22], Configuration Interaction [23], time independent perturbation theory [24], linear and non-linear variational method [24][25][26][27][28][29][30][31][32][33][34][35], Lagrange mesh method [36], B-splines [37], variational quantum Monte Carlo [38,39] and density functional theory [40][41][42]. Most of these studies have been devoted to the total energy calculations, correlation energy due to the radial and angular contribution of trial wave functions [31,32], polarizability, critical cage radius and so forth, as a function of the confining radius.…”