THEORETICAL-STUDIES ON THE STRUCTURE OF THE ENDOHEDRAL COMPLEXES NA-AT-C60 AND NA-AT-C70

On the basis of the Su-Schrieffer-Heeger model and the analysis of the physical pictures of the so-called endohedral complexes Na @C60 and N a @C70, which consist of C60 and C70 molecules and a sodium ion or ato m trapped inside, we have introduced two reasonable terms in the Hamil tonian to describe the interaction between the metal ion and the fulle rene cage. From this simple Hamiltonian, we can reproduce the results of other first-principles calculations. Using the simplex optimization method, we have calculated the lattice distortions when all carbon at oms relax, and their effect on the potential-energy curve. Our results show that this effect is large and important. We discuss the physical meaning of our results.