CALCULATION OF ENERGY AND CHARGE-TRANSFER OF THE MERCURY GRAPHITES KHGC4 AND RBHGC4 USING A QUANTUM METHOD

Using a quantum method, we have evaluated the charge transfers X(C), X (Hg), and X(K) or X(Rb) for the compounds KHgC4 and RbHgC4, studied in the forms K(+Xk)Hg(-XHg)(C(-XC))4 and Rb(+XRb)Hg(-XHg)(C(-XC))4, resp ectively. This energy is the sum of all the contributions from the act ion of the potential of each atom of the compound on all the others su rrounding it, until convergence is obtained. The potential takes into account the type of atom (atomic number and radius, etc.) as well as t he electronic configuration. To do so we have calculated the energy of the compounds as a function of the three non-independent variables (0 less-than-or-equal-to X(M) less-than-or-equal-to 1, 0 less-than-or-eq ual-to X(Hg) less-than-or-equal-to 1 and 0 less-than-or-equal-to X(C) less-than-or-equal-to 1/4), the three variables being related to each other only through the neutrality condition, X(M) - X(Hg) - 4X(C) = 0. The energy of the compound is then calculated for each combination of values respecting the neutrality of the lattice; the energy minimum t hen furnishes the most stable form of the compound and the correspondi ng values of charge transfer. We have also calculated the cohesive ene rgies of these compounds by calculating the energy balance leading to formation of the compound in which all the different steps are differe ntiated: change in graphene stacking sequence, increase in distances d (cc) and d(pp), sublimation of the metal and the mercury, and finally, ionization of the ensemble. We discuss these various results.