S. Doyenlang et al., CALCULATION OF ENERGY AND CHARGE-TRANSFER OF THE MERCURY GRAPHITES KHGC4 AND RBHGC4 USING A QUANTUM METHOD, Carbon, 32(6), 1994, pp. 1059-1065
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.