anisotropic Debye temperatures in reciprocal-space calculations
Dear FEFF users! I am looking into the use of the DEBYE card in order to calculate the EELS spectrum of graphite at ~800 K. Obviously, graphite is highly anisotropic, such that it would be unphysical to use a single Debye temperature. However, the effective in-plane (a,b axes) and out-of-plane (c axis) Debye temperatures are known for graphite (2500 and 950 K, respectively). I was therefore wondering whether it is possible in FEFF9 to specify two Debye temperatures for the two different crystallographic directions. I am calculating the (oriented) EELS spectrum of graphite in reciprocal space using the RECIPROCAL, LATTICE and ATOMS cards; see feff.inp file below. I am using FEFF version 9.05. In case the use of Debye temperatures is not possible in this way, could anybody recommend another way to take into account the Debye-Waller factors for an anisotropic material such as graphite? Thanks! Best regards, Renske van der Veen -- Dr. Renske M. van der Veen California Institute of Technology Arthur Amos Noyes Laboratory of Chemical Physics 1200 E California Blvd MC 127-72, Pasadena, CA 91125, USA Office: (+1) (626) 395 6530 Mobile: (+1) (626) 808 2635 **** TITLE graphite * C K edge energy = 284.20 eV EDGE K 0.0 CONTROL 1 1 1 1 1 1 PRINT 1 1 1 1 1 1 COREHOLE RPA LDOS -20 10 0.05 * this calculates the density of states EGRID e_grid -3 17 0.3 e_grid last 30 0.4 e_grid last 58 1 ELNES 200 # beam energy in keV 0 0 1 # beam direction in the crystal frame 10 5 # collection semiangle, convergence semiangle (in mrad) 200 1 # q-integration mesh : radial size, angular size 0.0 0.0 # position of the detector (x,y angle in mrad) FMS 7.0 2 EXCHANGE 0 1 0.7 SCF 5 RPATH 0.2 POTENTIALS * ipot Z element l_scmt l_fms stoichiometry 0 6 C 3 2 0.01 1 6 C 3 2 2 2 6 C 3 2 2 RECIPROCAL KMESH 5000 MARKER 1 LATTICE P 2.4612 0.86603 -0.50000 0.00000 0.00000 1.00000 0.00000 0.00000 0.00000 2.72546 ATOMS * this list contains 251 atoms * * x y z ipot tag distance 0.00000 0.00000 0.68160 1 C1 0.00000 0.00000 2.04479 1 C1 0.57735 0.00000 0.68160 2 C2 0.28868 0.50000 2.04479 2 C2 END
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Van Der Veen, Renske M.