The kernel of TOSCA is formed by a set of fortran routines that allow an ab initio non-SCF calculation by diagonalizing the Kohn-Sham hamiltonian using one of the following methods: full or partial diagonalization, diagonalization using the method of Lanczos, and Arnoldi diagonalization.
Once the eigenvalues and eigenvectors have been computed the following quantities can
be computed by TOSCA:
1) Slab polarizability computed with or without real space cutoff, for insulators, semiconductors, metals. Surface epsilon can be also computed;
2) Localization of the wavefunctions for given k-point(s) and states;
3) Squared modulus of a wavefunction for a given k-point and state on the real space FFT grid. Interface with DataExplorer for graphical representation by isosurfaces;
4) RAS (Reflectance Anisotropy Spectra) or SDR (Surface Differential Reflectivity).
TOSCA is interfaced in input with a local Car-Parinnello type code and with ABINIT, by reading the wavefunctions outputed by these codes. TOSCA can also output a Kohn-Sham structure file that can be used as input for an abinitio multipurpose Many-Body code SELF.
TOSCA contains 190 fortran routines. Routines are mainly written in f77. f90 routines assure the interfacing with other ab initio codes (ABINIT, ...).