Exercises core loss spectra WIEN2013 Penn State
General • MATERIALS • * TiN, TiC : see User’s Guide and previous exercises • * fcc Cu : a=6.822 a.u. ; space group = 225 ; Cu at 0.0 0.0 0.0 • * wurtzite GaN : H lattice, a=6.016, c=9.785 ; Ga at 1/3, 2/3, 0 and 2/3, 1/3, 0.5 ; N at 1/3, 2/3, u and 2/3, 1/3, u+1/2 (use u=0.371) • CALCULATION PARAMETERS • Use reasonable values. No need to use huge k-meshes or test RKMAX convergence at this point. (E.g. rkmax = 6 ; nkpt = 1000 ; or whatever you think is right). Use regular run_lapw for everything (no sp, so, …)
Cu K edge XAS • Set up a Cu calculation • Run SCF • Calculate the XAS for the K edge. The edge is at 8995 eV; core hole width is about 1.16 eV. • Compare to experiment below – why is it different?
h-GaN N K EELS • Set up a GaN calculation. Run the SCF. • Calculate the N K edge EELS, averaging over beam orientations. Use collection angle = 0.3 mrad, convergence angle = 0.2 mrad, beam energy = 300 keV. • Calculate orientation-sensitive spectra for a beam parallel to the c-axis ( 0 0 1) and for the beam in the a,b-plane (1 0 0). • Compare to blue curves below ( right: 1 0 0 ; left: 0 0 1)
Cu L3 corehole EELS • Make a small supercell from your previous Cu.struct (or remove symmetry from the regular unit cell) • Label 1 atom differently – this will be your core hole atom • Run initialization completely • Edit the case.inc and remove 1 electron from the 2p3/2 state • Either add 1 background charge in case.inm; or • add 1 valence electron in case.in2 (don’t do both!) • run SCF • calculate the L3 spectrum in TELNES • How does it compare to an L3 edge from your earlier ground-state calculation? • Repeat this exercise, but now remove only 0.5 electron from the core state.
GaN N K EELS • Create supercells of different size, e.g. 2x2x2 and 3x3x3 (and you can start with 1x1x1 if you like) • Compare the resulting N K spectra