Binary phosphorus-carbon compounds:: The series P4C3+8n

The structure and stability of periodic solid phosphorus carbide phases P4C3+8n (n = 0-4) are studied at zero and high pressure using periodic density functional theory as implemented in the codes SIESTA and CASTEP. For each composition a range of structures is examined, including both defective diamond-like and graphitic-like structures. At zero pressure the lowest energy structure for P4C3(n = 0) is defect zinc blende, whereas for compositions richer in carbon (n > 0) defect graphitic phases in which some carbon atom are bonded to three phosphorus neighbors are the most stable. We relate the relative stability of the different structures to the bonding and compare the corresponding nitrogen analogues. (C) 2003 Wiley Periodicals, Inc.