February 3, 1999 17:44 WSPC/140-IJMPB 3sc0040 International Journal of Modern Physics B, Vol. 12, Nos. 29, 30 & 31 (1998) 3091–3094 c  World Scientific Publishing Company A TWO-DIMENSIONAL STRUCTURE FACTOR CALCULATION FOR THE Cu-1 PLANE IN YBa 2 Cu 3 O 6 TANER EDIS * , J. D. FAN, D. BAGAYOKO and J. T. WANG Department of Physics, Southern University and A&M College Baton Rouge, Louisiana 70813, USA Received 1 April 1998 Revised 22 May 1998 The anisotropic radial distribution function and two-dimensional (2D) structure factor was calculated for the Cu-1 plane in YBa 2 Cu 3 O 6+x when x ≈ 0, based on data generated by a molecular dynamics simulation. The results indicate a stable square lattice and support the validity of layered two-dimensional screened Coulomb potential used in the simulation. 1. Introduction Atomistic simulations are widely used to study the structure of perovskite-type ox- ides, including high temperature superconducting materials. Typically, interatomic forces are modeled by pair potentials of the Buckingham type, 1– 4 V ij (r)= Z i Z j e 2 r + A ij e −r/ρ - C ij 1 r 6 (1) including, occasionally, three-body interactions to fix bond angles. Such techniques reproduce crystal structure accurately and are highly successful in approaching problems like defect properties or oxygen diffusion mechanisms. 4 However, since the potentials employed are not microscopically-based and depend on adjustable parameters for each type of bond, they are of limited use studying the interactions within high-T c materials. Some theories of superconductivity, especially those which ascribe a significant role to Coulomb interactions, have implications for the form of forces. They might be tested indirectly by studying whether they lead to a microscopically-based explanation of material structure. 2. MD Simulation High-T c materials are notable for their layered nature, thus it might be possi- ble to improve our interionic potentials by departing from the commonly used * E-mail: edis@phys.subr.edu 3091