THEORETICAL DETERMINATION OF THE LATTICE DYNAMICAL PROPERTIES OF THE MERCURY BASED SUPERCONDUCTOR HGBA2CUO4

A theoretical study of the lattice dynamical properties for the high t emperature superconductor HgBa2CuO4 is made within the framework of th e shell model. A frozen-phonon first principles determination of frequ encies and eingevectors of the Raman active modes is also made. We com pare these results with the recent Raman and neutron scattering experi mental work and use them to obtain insight for a possible clarificatio n of mode assigment. The origen of the 570 cm(-1) shoulder peak that a ppears in the low frequency side of the oxygen A(1g) peak is discussed althought an unambiguous distinction of this A(1g) like defect mode i s not possible at present.