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OPTIC (calculating optical properties)

Robert Abt and Claudia Ambrosch-Draxl
Institut für Theoretische Physik
Universität Graz
Universitätsplatz 5
A-8010 Graz, AUSTRIA
email: claudia.ambrosch@kfunigraz.ac.at

The calculation of optical properties requires a dense mesh of eigenvalues and the corresponding eigenvectors. For that purpose start KGEN and generate a fine k-mesh (with many k-points). Run lapw1 and then lapw2 with the option FERMI (Note: You must also put TETRA or ROOT/ALL in case.in2) in order to generate the weight-file. After the vector-file has been generated by lapw1 run optic in order to produce the momentum matrix elements. Then the program joint carries out the BZ integration and computes the imaginary part of the complex dielectric tensor. In order to obtain the real part of the dielectric tensor kram may be executed which by use of the Kramers-Kronig relations.

The program optic generates the momentum matrix elements

Pi $ {\bf P}_i = <n^{\prime}{\vec k} \vert {\vec p}.{\vec e}_i \vert \ n{\vec k}> $

between all band combinations for each k-point given in the vector-file. For the cases where ORTHO is true the squared diagonal components can be found in the file case.outmat. For non-orthogonal systems all 6 components (Mj)* Mk are written. In systems without inversion symmetry the complex version opticc must be executed.

For the calculation of the imaginary part of the dielectric tensor (in absence of spin-orbit coupling) up to 6 real components of the matrix elements can be calculated according to the symmetry of the crystal.

The dielectrid tensor components (and other quantities) are given per spin in case of the spin-polarized calculation and as a sum of both spin directions if thecalculation is non-spinpolarized.

Due to spin-orbit coupling imaginary parts of the nondiagonal elements may occur. This in general, up to 9 components can be calculated at the same time.



 
next up previous contents
Next: Execution Up: Programs for analysis, calculation Previous: Input

2000-04-11