[Pw_forum] STM code questions
David Pullman
dpullman at mail.sdsu.edu
Sun Jun 16 02:11:05 CEST 2013
Hello,
I’m trying to modify stm.f90 in order to
implement Julian Chen’s “derivative rule” for
simulating STM images. For example, if the
active orbital of the tip is pz, the contribution
of each surface state to the STM signal is
proportional to the square of the z-derivative
|dpsi/dz|^2, where psi is the surface wavefunction.
Before I get too far, I have two questions about the code:
1) The wavefunction (psic) is stored in a 1-D
array. After psic has been transformed to real
space, does the index run over a, then b, then c
(a,b,c are the lattice vectors)? That
is: a1,b1,c1
an,b1,c1; a1,b2,c1
an,b2,c1;
a1,bn,c1
an,bn,c1; a1,b1,c2
an,b1,c2;
2) There’s a comment at the beginning of
stm.f90, “It may not properly work if the slab
has two symmetric surfaces.” Why would symmetric surfaces present a problem?
Thanks,
David Pullman
Department of Chemistry and Biochemistry
San Diego State University
San Diego, CA 92182-1030
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