On variational solution of the four-body Santilli-Shillady model of $H_2$ molecule

In this paper, we apply Ritz variational approach to a new isochemical model of $H_2$ molecule suggested by Santilli and Shillady. We studied Gaussian, $V_g$, and exponential, $V_e$, screened Coloumb potential {\it approximations}, as well as the original Hulten potential, $V_h$, case. Both the Coloumb and exchange integrals have been calculated only for $V_e$ owing to Gegenbauer expansion while for $V_g$ and $V_h$ cases we achieved analytical results only for the Coloumb integrals. We conclude that the $V_e$-based model is capable to fit experimental data on $H_2$ molecule in confirmation of the results of numerical HFR approach by Santilli and Shillady. Also, we achieved the energy-based estimation of the weight of the isoelectronium phase which is appeared to be of the order of 1%...6%, for the case of $V_e$. However, we note that this is {\it not} the result corresponding to the original Santilli-Shillady model, which is based on the Hulten potential $V_h$. An interesting result is that in order to prevent divergency of the Coloumb integral for $V_h$ the correlation length parameter $r_c$ should run discrete set of values. We used this condition in our $V_e$-based model.