Energetics, electronic states, and magnetism of iron phthalocyanine on pristine and defected graphene layers

Abstract

Transition metal phthalocyanines (TMPc's) are under intense scrutiny in the field of spintronics, as they may be promising storage devices. The simplicity and cheapness of such molecules increase their commercial potential. There is an active study of how the magnetic moment of the metal centre of such molecules can be changed. Here, we particularly consider the iron phthalocyanine molecule (FePc) on a graphene layer as a substrate. We study how graphene defects (the Stone-Wales defect, B-doping, N-doping, S-doping, and combined B (N, S)-doped Stone-Wales defects) change the FePc electronic structure. We present ab initio study of the systems, which is done using several approaches: based on periodic plane wave density functional theory (DFT), a linear combination of atomic orbitals (LCAO) DFT with a cluster representation of graphene, and multiconfigurational methods with the pyrene molecule presented as a miniaturised graphene cluster. The treatment of the FePc/Graphene hybrid system using multiconfigurational methods was done for the first time. It was found that the hybrid systems with B- and N- dopings have quasi-degenerate ground states and it is necessary to go beyond the approximation of one Slater determinant.