Scopes of computation: Things one can compute using our codes.

Codes are interfaced with a version of Quantum Espresso.
Primary imput to our codes are the Kohn-Sham states and the corresponding eigenvalues.

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Codes perform two types of calculations:
A. Construction of Wannierized hybrid atomic orbital basis from first principles and various computations in the Wannierized basis.

B. Computation of Berry phase and Wannier centres

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Steps of calculation:

A. Constructuion of Wannierized hybrid atomic orbital basis :
Click on the items (if active) of input variables and execution.

1. Deciding the variety of the hybrid atomic orbital basis:
Identification of inequivalent atoms in the given system in terms of element type and relative orientations of nearest neighbour coordinations. Depending on the nearest neighbourhood we need to decide on the nature of the hybrid basis and whether a degenerate hybrid basis is sufficient (as in case of ideal bond angles) or we need a non-degenerate hybrid basis.

2. Construction of hybrid atomic orbital(HAO) basis
2a. Construction of degenerate hybrid atomic orbitals(HAO) for atoms
2b. Construction of non-degenerate / maximally valent HAO for atoms.

         Related scopes :
         2c. Template free construction of maximally localized Wannier function(MLWF) in isolated systems.

3. Construction of non-orthogonal basis template for a given system
Transferring and orienting HAOs from isolated atoms to all the atoms of the given system through mapping of neighborhood

4. Construction of hybrid atomic Wannier orbital(HAWO) basis
4a. Wannierization of the KS states based on the non-orthogonal template, leading to construction of the HAWOs and the tight-binding Hamiltonian in the HAWO basis

         Related scopes :
         4b. Template based construction of Wannier function representation of occupied states.

5. Post-processing in HAWO basis
5a. TB-band-structure, TB-DOS, HAWO-PDOS, bond-order, population analysis etc.

5b. Mean-field hubbard model calculation in HAWO basis.

5c. Optical absorption from real time dynamics in HAWO basis.

5d. Quantum transport in HAWO basis.

5e. Transfer of TB parameters from reference systems to larger target systems to perform 5b,5c,5d in large systems.

5e also enables estimation of quasi-particle gap of large systems at the level of DFT+GW through mapping of self-energy corrected TB parameters in HAWO basis.

5c followed by 5e enables realistic estimation of optical absorption threshold of large systems.

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B. Computation of Berry phase and Wannier centres

6a Computation of hermaprodite Wannier centres(HWC) localized along a given direction
6b Computation of maximally joint Wnnier centres(MJWC) in three dimensions

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Codes to construct the degenerate HAOs in step 2a, and the following steps 3,4a,4b,5a are provided under the COMPULSORY section in the download page.
Extra codes required to compute the non-degenerate and maximally valent HAOs in step 2b are provided under the OPTIONAL section of the download page.

Codes for 5b,5d,5e are available under the OPTIONAL section in the download page.

Sample input files and instruction on sequence of calculations are available in the individual links.