[TCOD] Brillouin zone integration tags

[Andrius Merkys]

Hi all,

after a very interesting discussion with Giovanni Pizzi yesterday I
have prepared a list of proposed additions/modifications to the
cif_dft.dic concerning the Brillouin zone integration:

1) Redefine tag '_dft_BZ_integration_method' (currently a free text
tag) as an enumeration list with values:

* 'simple sampling'
* 'linear tetrahedron'
* 'weighted tetrahedron' (see Blöchl et al. 1994)
* 'Monkhorst-Pack'
* 'other' (method name given in a new tag
'_dft_BZ_integration_method_other_name')

Can we list some more widely-used methods? By the way, does
'Monkhorst-Pack' belong here or should better be an option for
'_dft_BZ_integration_grid_type' tag?

2) Redefine tags '_dft_BZ_integration_grid_shift_[XYZ]' (free text
tags currently) as numeric with value ranges of [0,1).

3) Add a loop to list irreducible BZ points in tags
_dft_BZ_integration_grid_IBZ_point_{id,x,y,z,weight}, weights being
normalized (0 <= weight <= 1)

4) Add _dft_BZ_integration_smearing_method with following possible values:

* 'gaussian'
* 'Methfessel-Paxton'
* 'Marzari-Vanderbilt'
* 'Fermi-Dirac'
* 'other' (method name given in new tag
'_dft_BZ_integration_smearing_method_other_name')

Maybe there are more smearing methods to add?

Looking forward for your comments,
Andrius Merkys