PROGRAM SUMMARY
Title of program:
BEEM
Catalogue identifier:
ADLR
Ref. in CPC:
127(2000)327
Distribution format: gzip file
Operating system: OSF1 DEC-Unix v4.0
High speed store required:
32MK words
Number of bits in a word:
64
Peripherals Required: disc
Number of lines in distributed program, including test data, etc:
17633
Programming language used: Fortran
Computer: Alpha DEC 3000/400
Nature of physical problem:
We describe the Fortran-90 program BEEM v2.1 for the computation of real
and reciprocal space currents in Ballistic Electron Emission Microscopy
(BEEM), and Spectroscopy (BEES) [1-4].
Method of solution
Based on a LCAO Hamiltonian, the equilibrium one-particle Green's
Functions of a semi-infinite crystal are obtained using a decimation
technique. By means of Keldysh's formalism, the STM tip is coupled to
this crystal, and expressions for BEEM currents in real and reciprocal
space are obtained. Finally, a Dyson-like equation and a
self-consistent charge neutrality condition are applied to incorporate
reconstructed or relaxed layers in the surface region.
Typical running time
The test run took about 1 hr for Au and about 6 hrs for CoSi2 (once the
decimation is stored, the run takes around 0.5-0.6 hrs for both Au and
CoSi2).
References
[1] F.J. Garcia-Vidal, P.L. de Andres and F. Flores, Phys. Rev. Lett.
76, 807 (1996).
[2] P.L. de Andres, F.J. Garcia-Vidal, D. Sestovic and F. Flores, Phys.
Scripta T66, 277 (1996).
[3] K. Reuter, P.L. de Andres, F.J. Garcia-Vidal, D. Sestovic, F. Flores
and K. Heinz, Phys. Rev. B 58, 14036 (1998).
[4] K. Reuter, F.J. Garcia-Vidal, P.L. de Andres, F. Flores and
K. Heinz, Phys. Rev. Lett. 81, 4963 (1998).