HR: 0830h
AN: V11D-0524    [PDF]
TI: Finite-temperature Properties of bcc Fe
AU: * Shook, D
EM: dshook@andrew.cmu.edu
AF: Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213 United States
AU: Pellab, S
EM: s.pella@gl.ciw.edu
AF: Carnegie Institute of Washington, 5251 Broad Branch Rd., N.W,, Washington, DC 20015 United States
AU: Wu, Z
EM: z.wu@gl.ciw.edu
AF: Carnegie Institute of Washington, 5251 Broad Branch Rd., N.W,, Washington, DC 20015 United States
AU: Cohen, R
EM: cohen@gl.ciw.edu
AF: Carnegie Institute of Washington, 5251 Broad Branch Rd., N.W,, Washington, DC 20015 United States
AB: We have used a tight-binding model fit to first-principles linearized augmented plane wave computations to compute finite temperatures magnetic properties of bcc Fe. The tight-binding model was used to compute total energies and magnetic fields as functions of magnetic moment for ferromagnetic and antiferromagnetic spin arrangements. The derived energies were used to fit parameters for an effective Hamiltonian whose energy could be evaluated very rapidly. We used an energy expression (slightly modified) from Rosengaard and Johansson (PRB 55, 14975, 1997). This effective Hamiltonian contains onsite terms which are functions of moment, and Heisenberg-like interactions, which are functions of the moments on a pair of atoms. We have performed a preliminary parametrization for first-neighbors and including only m$_i\cdot$m$_j$ interaction terms. Monte Carlo simulations (800,000 steps per run) using the Metropolis algorithm were performed using this effective Hamiltonian for supercells of 128 atoms. As the temperature increased the total magnetic moment of the system decreased to zero, yielding the Curie temperature, Tc. Preliminary results for -27, and -1 GPa are 1000 and 800K, respectively. This model will be used to find the magnetic contributions to the equation of state.
DE: 3924 High-pressure behavior
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting