SYNTHESIS AND STUDY OF THE ELECTRONIC-STRUCTURE OF MOLYBDENUM TETRASULFIDE AND ITS LITHIUM INTERCALATES

An X-ray amorphous phase with the analytical formula MoS4 was synthesi zed. The quantum chemical simulation of the suggested local structure of MoS4 and calculation of the electronic structure of the finite chai n cluster [Mo-5(S-4)(6)](4-), as well as the fragmental analysis of co mposition of molecular orbitals (MO) of the cluster, have been perform ed by the EHMO technique. The electronic structure of molybdenum tetra sulfide and its lithium intercalates has been studied by X-ray emissio n and X-ray electron spectroscopies. It is shown that the low free orb itals contain contributions of molybdenum and sulfur atoms and are ant ibonding in nature. The occupation of these orbitals by the electrons of inserted lithium atoms leads to the weakening of the Mo-S bonds and to destructive changes of the matrix. The change of electronic struct ure of initial molybdenum tetrasulfide under intercalation of up to fo ur lithium atoms per formula unit can be interpreted on the basis of t he rigid band model. Further intercalation of up to seven atoms per fo rmula unit probably leads to a destructive change of the one-dimension al structure of the matrix. (C) 1997 Elsevier Science Ltd. All rights reserved.