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Epsilon code overview

Epsilon is the name of the code that generates the polarizability matrix and the inverse dielectric matrix for a bulk or nanoscale system. The main result of the epsilon code is the generation of the epsmat[.h5] and eps0mat[.h5] files which can be used in a Sigma or BSE calculation.

Summary of input and output files

Required input files

  • epsilon.inp: Input parameters.

  • WFN: This is linked to the unshifted grid. Information of spinor wavefunctions is initialized automatically.

  • WFNq: This is linked to the shifted grid. When a shift is not required, this can be the same file as WFN. This happens for calculations on:

    • semiconductors with spherical or box truncation;
    • metals / graphene-like screening with the is_q0 flag set to 2.

Auxiliary input files

These files are output files from previous runs, and may be used as input to speed up calculation:

  • chimat[.h5]: Polarizability matrix for q\ne0. No need to recalculate matrix elements. The file has a .h5 extension if the code is compiled with HDF5 support (for specification, see epsmat.h5.spec).

  • chi0mat[.h5]: Polarizability matrix for q\rightarrow0. No need to recalculate matrix elements. The file has a .h5 extension if the code is compiled with HDF5 support (for specification, see epsmat.h5.spec).

The files below are used if eqp_corrections is set in epsilon.inp. The corrected eigenvalues are used for constructing the polarizability matrix.

  • eqp.dat: A list of quasiparticle energy corrections for the bands in WFN.
  • eqp_q.dat: A list of quasiparticle energy corrections for the bands in WFNq.

Output Files

  • espmat[.h5]: Inverse dielectric matrix for q\ne0. The file has a .h5 extension if the code is compiled with HDF5 support (for specification, see epsmat.h5.spec).

  • eps0mat[.h5]: Inverse dielectric matrix for q\rightarrow0. The file has a .h5 extension if the code is compiled with HDF5 support (for specification, see epsmat.h5.spec).

  • epsilon.log: The log file containing values of chimat and epsmat.

  • chi_converge.dat: Convergence chi with respect to empty orbitals. Columns:

    • number of conduction bands;

    • \mathrm{Re}\, \chi(G=G'=0,q), extrapolated \mathrm{Re}\,\chi(G=G'=0,q);

    • \mathrm{Re}\, \chi(G=G'=G_\mathrm{max},q), extrapolated \mathrm{Re}\,\chi(G=G'=G_\mathrm{max},q).