Table of=20 Contents

Specification=20 of the XSF = Format
   =20 Introduction=20 to XSF = format
   =20 Comment=20 lines
    = Specification=20 of Molecular=20 Structure
   =20 Specification=20 of Periodic=20 Structures
   =20 Specification=20 of Forces
   =20 Specification=20 of Animated XSF=20 format
   =20     Animated=20 XSF for molecules
   =20     Animated=20 XSF for periodic = structures
   =20         Fixed-cell=20 animated XSF
    =    =20     Variable-cell=20 animated XSF
    = Specification=20 of 2D and 3D=20 = scalar-fields
   =20     General=20 vs. Periodic grids
   =20     Datagrids
   =20     Bandgrids=20 (visualization of Fermi=20 surfaces)

Specification of the XSF = Format

Introduction to XSF = format

The XSF=20 format is internal XCrySDen structure = format. XSF=20 stands for XCrySDen=20 Structure File. It is used to describe (i) molecular = and=20 crystal structure, (ii) forces acting on constituent = atoms, and=20 (iii) scalar fields (for example: charge density, = electrostatic=20 potential). The main attributes of XSF format are:=20

all records are in free format=20
the XSF formatted file is composed from various = sections=20
each sections begins with the keyword=20
there are two types of keywords: (i) single = keywords, and (ii) sandwich keywords, which are = defined=20 as:=20
- single keyword: section begins with a = single=20 keyword and ends without an end-keyword=20
- sandwich keyword: section begins with a=20 begin-keyword (i.e. BEGIN_keyword) and = ends with=20 an end-keyword (i.e. END_keyword), where=20 keyword is one among keywords.
all coordinates are in ANGSTROMS units=20
all forces are in Hartree/ANGSTROM units=20
the comment-lines start with the "#" character (see = below)=20

Comment lines

The = comment-lines were=20 introduced to the XSF file starting from XCrySDen version 1.4. = The=20 comment-lines start with the "#" character; = comments are=20 allowed only between sections and not within a given = section. Here=20 are two examples (correct and incorrect).=20

Correct example (comments are bewteen the = sections):

 # this is a specification=20
 # of ZnS crystal structure

 CRYSTAL

 # these are primitive lattice vectors (in Angstroms)

 PRIMVEC
    2.7100000000    2.7100000000    0.0000000000
    2.7100000000    0.0000000000    2.7100000000
    0.0000000000    2.7100000000    2.7100000000

 # these are convetional lattice vectors (in Angstroms)

 CONVVEC
    5.4200000000    0.0000000000    0.0000000000
    0.0000000000    5.4200000000    0.0000000000
    0.0000000000    0.0000000000    5.4200000000

 # these are atomic coordinates in a primitive unit cell=20
 # (in Angstroms)

 PRIMCOORD
 2 1
 16      0.0000000000     0.0000000000     0.0000000000
 30      1.3550000000    -1.3550000000    -1.3550000000
               =20

Incorrect=20 example (comment is within the section):=20

 ATOMS
  6    2.325243   -0.115261    0.031711
  1    2.344577   -0.363301    1.077589
#
# this is a comment on the wrong place
#
  6    0.007719   -0.041269    0.244204
  9    0.064656    1.154700    0.824420
  9   -0.042641   -0.911850    1.255074
  8   -1.071578   -0.152842   -0.539134
               =20

Specification of Molecular=20 Structure

For MOLECULES the XSF format is very = simple. The=20 first line begins with the ATOMS keyword and = then one=20 specifies the structural data for all atoms. An entry for = an atom=20 looks like:

 AtNum   X Y Z

where AtNum stands for atomic number (or=20 symbol), while X Y Z are Cartesian = coordinates in=20 ANGSTROMS units. Here is one example:=20

 ATOMS
  6    2.325243   -0.115261    0.031711
  1    2.344577   -0.363301    1.077589
  9    3.131708   -0.909527   -0.638930
  9    2.736189    1.130568   -0.134093
  8    1.079338   -0.265162   -0.526351
  6    0.007719   -0.041269    0.244204
  9    0.064656    1.154700    0.824420
  9   -0.042641   -0.911850    1.255074
  8   -1.071578   -0.152842   -0.539134
  6   -2.310374    0.036537    0.022189
  1   -2.267004    0.230694    1.077874
  9   -2.890949    1.048938   -0.593940
  9   -3.029540   -1.046542   -0.203665
               =20

Specification of Periodic=20 Structures

The XSF format allows to specify = structures of=20 different periodicity. The keywords MOLECULE, = POLYMER, SLAB, and = CRYSTAL=20 designate the 0-, 1-, 2-, and 3-dimensional structures = (i.e.=20 periodic dimensions are meant here). For crystal = structures the=20 file begin with CRYSTAL keyword. Then one = needs to=20 specify the lattice vectors and the atoms belonging to the = unit=20 cell. XCrySDen = accepts=20 two different setting of the unit cell. These are usually = called=20 the primitive and the conventional unit cell. The = corresponding=20 keywords are PRIMVEC for primitive lattice = vectors=20 and PRIMCOORD for atoms belonging to the = primitive=20 unit cell. The CONVVEC and = CONVCOORD=20 have the analogous meaning for the conventional unit cell. = Warning: in XSF file the two settings of the unit = cell are=20 supposed to have the same origin. If you want to specify = some=20 crystal structure with two settings of the unit cell, that = have=20 different origins you will have to create two XSF files. = In=20 practice only PRIMVEC, PRIMCOORD = and=20 CONVVEC need to be specified, and then = "conventional=20 coordinates" (CONVCOORD) are generated by = XCrySDen itself, = hence it is=20 never needed to specify the CONVCOORD = section=20 !!! Here is an example of ZnS crystal structure:=20

 CRYSTAL                                        see (1)
 PRIMVEC
    0.0000000    2.7100000    2.7100000         see (2)
    2.7100000    0.0000000    2.7100000
    2.7100000    2.7100000    0.0000000
 CONVVEC
    5.4200000    0.0000000    0.0000000         see (3)
    0.0000000    5.4200000    0.0000000
    0.0000000    0.0000000    5.4200000
 PRIMCOORD
 2 1                                            see (4)
 16      0.0000000     0.0000000     0.0000000  see (5)
 30      1.3550000    -1.3550000    -1.3550000

               =20

Legend:
(1)	this keyword specify the = structure is=20 crystal
(2)	specification of = `PRIMVEC` (in=20 ANGSTROMS)=20 = like: `ax, = ay, az` (first lattice=20 = vector) `bx= ,=20 by, bz` (second lattice=20 = vector) `cx= ,=20 cy, cz` (third lattice=20 vector)
(3)	specification of = `CONVVEC`=20 (see (2))
(4)	First number stands for number = of atoms=20 in the primitive cell (2 in this case). The second = number is=20 always 1 for `PRIMCOORD`=20 coordinates.
(5)	Specification of atoms in the = primitive=20 cell (the same as for `ATOMS`=20 section).

Specification of Forces

All = that is=20 needed to specify the forces acting on atoms is to = supplement the=20 appropriate coordinate section (ATOMS or=20 PRIMCOORD). Now an entry for an atom would = look like:=20

 AtNum   X Y Z   Fx Fy Fz

where Fx Fy Fz stands for force components in=20 X, Y and Z direction, respectively. The force components = are=20 expressed in Cartesian coordinate system in = Hartree/ANGSTROM unit.=20 Here is an example of water molecule:=20

 ATOMS
  8   0.00000  0.00000  0.00000   -.05164  .00000 -.03999
  1   0.00000  0.00000  1.00000    .01769  .00000  .03049
  1   0.96814  0.00000 -0.25038    .03395  .00000  .00949
                 =20

And here is an=20 example for the periodic structure structure:=20

 SLAB
 PRIMVEC
   5.8859828533     0.0000000000     0.0000000000
   0.0000000000     5.8859828533     0.0000000000
   0.0000000000     0.0000000000     1.0000000000
 PRIMCOORD 1
 11 1
  6    3.674759   2.942992  -3.493103     -0.021668   0.000000  =
-0.057324
  1    4.121990   3.816734  -4.007689     -0.000478   0.001204   =
0.006657
  1    4.121990   2.069250  -4.007689     -0.000478  -0.001204   =
0.006657
  6    2.211226   2.942992  -3.493103      0.021668   0.000000  =
-0.057324
  1    1.763995   3.816734  -4.007689      0.000478   0.001204   =
0.006657
  1    1.763995   2.069250  -4.007689      0.000478  -0.001204   =
0.006657
  8    0.000000   0.000000  -2.719012      0.000000   0.000000  =
-0.050242
 47    4.448147   4.449892  -1.919011     -0.022812  -0.029123   =
0.007553
 47    4.448147   1.436093  -1.919011     -0.022812   0.029123   =
0.007553
 47    1.437838   4.449892  -1.919011      0.022812  -0.029123   =
0.007553
 47    1.437838   1.436093  -1.919011      0.022812   0.029123   =
0.007553
                 =20

Specification of Animated XSF=20 format

It is possible to specify several snapshots = of a=20 structure in the XSF format. For example: the file can = contain the=20 data for all structures that were created during an = optimization=20 run or molecular-dynamics run. These structures can be = displayed=20 as animation by XCrySDen.=20 The main attributes of the animated XSF format are:=20

the AXSF file begins with the ANIMSTEPS=20 nstep keyword, where = nstep=20 stands for number of animation steps.=20
number of atoms for all steps must be the = same=20 !!!=20
in fixed-cell animated XSF for crystal structures = the unit=20 cell for all steps is taken to be the same=20
in variable-cell animated XSF for crystal structures = the=20 unit cell is specified for each animation step=20
the ATOMS and PRIMCOORD = keywords=20 are prefixed by an integer number which is the = sequential index=20 of a given snapshot. Therefore the syntax is ATOMS = istep and PRIMCOORD = istep.=20
for variable-cell crystal structure the = PRIMVEC=20 and CONVVEC keywords are prefixed with = sequential=20 index.

Animated XSF for = molecules

Here is an=20 example of AXSF file. It shows different structures during = an=20 optimization of water molecule. Note the index prefixes = after=20 ATOMS keywords.=20

 ANIMSTEPS 4
 ATOMS 1
  8    0.0000  0.0000  0.0000     -0.0516  0.0000 -0.0399
  1    0.0000  0.0000  1.0000      0.0176  0.0000  0.0304
  1    0.9681  0.0000 -0.2503      0.0339  0.0000  0.0094
 ATOMS 2
  8   -0.1480  0.0000 -0.1146      0.0020  0.0000  0.0015
  1   -0.0468  0.0000  0.9134     -0.0069  0.0000  0.0069
  1    0.8726  0.0000 -0.2740      0.0049  0.0000 -0.0084
 ATOMS 3
  8   -0.1032  0.0000 -0.0799      0.0013  0.0000  0.0010
  1   -0.0319  0.0000  0.9591      0.0011  0.0000 -0.0028
  1    0.9205  0.0000 -0.2710     -0.0025  0.0000  0.0018
 ATOMS 4
  8   -0.1102  0.0000 -0.0853      0.0001  0.0000  0.0000
  1   -0.0345  0.0000  0.9503     -0.0000  0.0000 -0.0000
  1    0.9114  0.0000 -0.2714     -0.0000  0.0000 -0.0000
                   =20

Animated XSF for periodic = structures

Fixed-cell animated = XSF

Here is an=20 example of animated XSF for the ZnS crystal structure with = the=20 fixed unit-cell. Note the index prefixes after=20 PRIMCOORD keywords.=20

 ANIMSTEPS 2
 CRYSTAL
 PRIMVEC
    0.0000000    2.7100000    2.7100000   =20
    2.7100000    0.0000000    2.7100000
    2.7100000    2.7100000    0.0000000
 PRIMCOORD 1
    2 1                                          =20
    16      0.0000000     0.0000000     0.0000000=20
    30      1.3550000    -1.3550000    -1.3550000
 PRIMCOORD 2
    2 1                                          =20
    16      0.0000000     0.0000000     0.0000000=20
    30      1.2550000    -1.2550000    -1.2550000
                   =20

Variable-cell animated = XSF

Here is=20 an example of animated XSF for the ZnS crystal structure = with the=20 variable unit-cell. Note the index prefixes after=20 PRIMVEC, CONVVEC, and=20 PRIMCOORD keywords.=20

 ANIMSTEPS 2
 CRYSTAL
 PRIMVEC 1
    2.7100000    2.7100000    0.00000000
    2.7100000    0.0000000    2.71000000
    0.0000000    2.7100000    2.71000000
 CONVVEC 1
    5.4200000    0.0000000    0.00000000
    0.0000000    5.4200000    0.00000000
    0.0000000    0.0000000    5.42000000
 PRIMCOORD 1
    2 1
    16      0.0000000     0.0000000     0.00000000
    30      1.3550000    -1.3550000    -1.35500000
 PRIMVEC 2
    2.9810000    2.9810000    0.00000000
    2.9810000    0.0000000    2.98100000
    0.0000000    2.9810000    2.98100000
 CONVVEC 2
    5.9620000    0.0000000    0.00000000
    0.0000000    5.9620000    0.00000000
    0.0000000    0.0000000    5.96200000
 PRIMCOORD 2
    2 1
    16      0.0000000     0.0000000     0.00000000
    30      1.5905000    -1.5905000    -1.59050000
                   =20

Specification of 2D and 3D=20 scalar-fields

It is possible to specify one or = several=20 scalar fields (both 2D and 3D) as an uniform mesh = of values=20 in the XSF formatted file. The mesh can be = non-orthogonal.=20 This scalar field meshes are called datagrids.

General vs. Periodic = grids

Datagrids=20 in XCrySDen are = general=20 grids and not periodic one!!! What is meant by this will = be=20 explained bellow. A general grid is a uniform grid that is = spanned=20 inside some box, which is either non-orthogonal or = orthogonal. For=20 a molecule such a box would be a bounding box, while for = crystal=20 such a box would be a unit cell. However in a grid that = span a=20 whole unit-cell some border points would be redundant due = to=20 translational symmetry. Grids that omit these redundant = points are=20 called periodic (by this convention a FFT (fast-Fourier = transform)=20 mesh would be a periodic mesh). The general vs. periodic = grid=20 concept is shown graphically here:=20

N= ote:=20 datagrids in XCrySDen are=20 general grids !!!=20

Datagrids

The datagrid = section is=20 structured and organized in blocks. The grids inside a = block can=20 be manipulated among themselves by XCrySDen program. The = main=20 attributes of XSF datagrids are:=20

(1)	the top datagrid section is = called=20 BLOCK_DATAGRID and is sandwiched between=20 `BEGIN_BLOCK_DATAGRID_xD` and=20 `END_BLOCK_DATAGRID_xD` keywords, where=20 `x` stands for the dimensionality of the = grid.=20 Currently 2D and 3D scalar grids are = supported.
(2)	there can be an arbitrary = number of=20 BLOCK_DATAGRID sections.
(3)	there can be an arbitrary = number of=20 datagrids inside one BLOCK_DATAGRID section. All = datagrids=20 belonging to the same BLOCK_DATAGRID must have the=20 dimensionality as defined by=20 `BEGIN_BLOCK_DATAGRID_xD` keyword. These=20 datagrids must also share the following properties: = (i) they=20 should span the same space (origin and the spanning = vectors=20 must be the same), and (ii) they should have the = same number=20 of data-points. Each datagrid in a BLOCK_DATAGRID is = sandwiched inside = `BEGIN_DATAGRID_xD_identifier`=20 and `END_DATAGRID_xD` keywords, where=20 `x` stands for dimensionality of the grid = and the=20 `identifier` is used as an identifier of = the=20 datagrid.
(4)	after the=20 `BEGIN_BLOCK_DATAGRID_xD` keyword and = before the=20 first `DATAGRID_xD_identifier` keyword is = a=20 comment, which is used as an identifier for the=20 BLOCK_DATAGRID. It must be a single=20 word!!!
(5)	the values inside a datagrid = are=20 specified in column-major (i.e. FORTRAN) order. This = means=20 that values are written as:=20 C-syntax: for (k=3D0; k<nz; k++) for (j=3D0; j<ny; j++) for (i=3D0; i<nx; i++) printf("%f",value[i][j][k]); FORTRAN syntax: write(,) $ (((value(ix,iy,iz),ix=3D1,nx),iy=3D1,ny),iz=3D1,nz)

Above=20 specifications may sound very fuzzy, hence let us clarify = this by=20 looking at a very simple example. The descri= ption=20 of all records follows after the example. Also take a look = at schematic=20 presentation of the structure of datagrids of below = example.=20

l.01
l.02
l.03
l.04
l.05
l.06
l.07
l.08
l.09
l.10
l.11
l.12
l.13
l.14
l.15
l.16
l.17
l.18
l.19
l.20
l.21
l.22
l.23
l.24
l.25
l.26
l.27
l.28
l.29
l.30
l.31
l.32
l.33
l.34
l.35
l.36
l.37
l.38
l.39
l.40
l.41
l.42
l.43
l.44
l.45
l.46
l.47
l.48
l.49
l.50
l.51
l.52
l.53
l.54
l.55
l.56
l.57
l.58
l.59
l.60
l.61
l.62
l.63
l.64
l.65

 BEGIN_BLOCK_DATAGRID_2D                =20
   my_first_example_of_2D_datagrid     =20
   BEGIN_DATAGRID_2D_this_is_2Dgrid#1          =20
     5  5                                =20
     0.0 0.0 0.0                         =20
     1.0 0.0 0.0                         =20
     0.0 1.0 0.0                         =20
       0.000  1.000  2.000  5.196  8.000 =20
       1.000  1.414  2.236  5.292  8.062       =20
       2.000  2.236  2.828  5.568  8.246       =20
       3.000  3.162  3.606  6.000  8.544       =20
       4.000  4.123  4.472  6.557  8.944       =20
   END_DATAGRID_2D                     =20
   BEGIN_DATAGRID_2D_this_is_2Dgrid#2          =20
     5  5                                      =20
     0.0 0.0 0.0                               =20
     1.0 0.0 0.0                               =20
     0.0 1.0 0.0                               =20
       4.000  4.123  4.472  6.557  8.944       =20
       3.000  3.162  3.606  6.000  8.544       =20
       2.000  2.236  2.828  5.568  8.246       =20
       1.000  1.414  2.236  5.292  8.062       =20
       0.000  1.000  2.000  5.196  8.000       =20
   END_DATAGRID_2D                     =20
 END_BLOCK_DATAGRID_2D                 =20
                                       =20
 BEGIN_BLOCK_DATAGRID_3D                       =20
   my_first_example_of_3D_datagrid     =20
   BEGIN_DATAGRID_3D_this_is_3Dgrid#1          =20
     5  5  5                             =20
     0.0 0.0 0.0                         =20
     1.0 0.0 0.0                         =20
     0.0 1.0 0.0                               =20
     0.0 0.0 1.0                         =20
       0.000  1.000  2.000  5.196  8.000       =20
       1.000  1.414  2.236  5.292  8.062       =20
       2.000  2.236  2.828  5.568  8.246       =20
       3.000  3.162  3.606  6.000  8.544       =20
       4.000  4.123  4.472  6.557  8.944       =20
                                       =20
       1.000  1.414  2.236  5.292  8.062       =20
       1.414  1.732  2.449  5.385  8.124       =20
       2.236  2.449  3.000  5.657  8.307       =20
       3.162  3.317  3.742  6.083  8.602       =20
       4.123  4.243  4.583  6.633  9.000       =20
                                       =20
       2.000  2.236  2.828  5.568  8.246       =20
       2.236  2.449  3.000  5.657  8.307       =20
       2.828  3.000  3.464  5.916  8.485       =20
       3.606  3.742  4.123  6.325  8.775       =20
       4.472  4.583  4.899  6.856  9.165       =20
                                       =20
       3.000  3.162  3.606  6.000  8.544       =20
       3.162  3.317  3.742  6.083  8.602       =20
       3.606  3.742  4.123  6.325  8.775       =20
       4.243  4.359  4.690  6.708  9.055       =20
       5.000  5.099  5.385  7.211  9.434       =20
                                       =20
       4.000  4.123  4.472  6.557  8.944       =20
       4.123  4.243  4.583  6.633  9.000       =20
       4.472  4.583  4.899  6.856  9.165       =20
       5.000  5.099  5.385  7.211  9.434       =20
       5.657  5.745  6.000  7.681  9.798       =20
   END_DATAGRID_3D                     =20
 END_BLOCK_DATAGRID_3D                  =20
                   =20

Legend:
l.01	beginning of 2D block of=20 datagrids
l.02	one word comment - used as an = identifier=20 for this block
l.03	beginning of the first 2D = datagrid in a=20 block
l.04	number of data-points in each = direction=20 (i.e. `nx ny` for 2D = grids)
l.05	origin of the = datagrid
l.06	first spanning vector of the=20 datagrid
l.07	second spanning = vector
l.08-12	5x5 datagrid values in = column-major=20 mode
l.13	end of the first 2D datagrid in = a=20 block
l.14-24	these lines specify second 2D = datagrid in=20 a block in totally analogous manner as the first 2D=20 datagrid.
l.25	end of 2D block of=20 datagrids

l.27	beginning of 3D block of=20 datagrids
l.28	one word comment - used as an = identifier=20 for this block
l.29	beginning of the first 3D = datagrid in a=20 block
l.30	number of data-points in each = direction=20 (i.e. `nx ny nz` for 3D = grids)
l.31	origin of the = datagrid
l.32	first spanning vector of the=20 datagrid
l.33	second spanning = vector
l.34	third spanning = vector
l.35-63	5x5x5 datagrid values in = column-major=20 mode
l.64	end of the first 3D datagrid in = a=20 block
l.65	end of 3D block of=20 datagrids

Here = is a scheme of=20 the structure of datagrids of above example as displayed = by XCrySDen program.

<= A=20 name=3Dbxsf>

Bandgrids (visualization of Fermi=20 surfaces)

Bandgrids are variation on a = theme of=20 datagrids. They were introduced for the visualization of = Fermi=20 surfaces and yields a simplified format of = datagrids.=20 Please notice that despite their purpose they are still general=20 grids and not periodic ones. The bandgrid for = the=20 visualization of Fermi surface should be defined as:=20

Please= =20 notice that the bandgrid span the reciprocal unit cell, = not the=20 Brillouin zone !!! Points are later translated back to = Brillouin=20 zone by XCrySDen and=20 Fermi surface is rendered inside the Brillouin zone.=20 Warning: so far XCrySDen uses=20 bandgrids solely for the visualization of Fermi = surfaces=20 (the coresponding files are called BXSF, standing for = Band-XSF).=20 If you want to render some other property as = contours/isosurfaces=20 you must specify the scalar fields as datagrids. = This is=20 because the Fermi surfaces needs some special processing = and=20 therefore bandgrids are automatically processed. The main=20 attributes of bandgrids are:=20

(1)	the structure of = bandgrids is=20 similar to datagrids
(2)	there can only be one = BLOCK_BANDGRID=20 section
(3)	there can only be one BANDGRID = in=20 BLOCK_BANDGRID
(4)	there can be an arbitrary = number of=20 bands inside BANDGRID section, where BAND = is=20 ...
(5)	so far only 3D bandgrids = are=20 supported
BEWARE:	the values inside a bandgrid = are=20 specified in row-major=20 (i.e. C) order. This means that values are written = as:=20 C-syntax: for (i=3D0; i<nx; i++) for (j=3D0; j<ny; j++) for (k=3D0; k<nz; k++) printf("%f",value[i][j][k]); FORTRAN syntax: write(,) $ (((value(ix,iy,iz),iz=3D1,nz),iy=3D1,ny),ix=3D1,nx)

Here is a=20 bandgrid example. The description of the records = is below=20 the example.=20

l.01
l.02
l.03
l.04
l.05
l.06
l.07
l.08
l.09
l.10
l.11
l.12
l.13
l.14
l.15
l.16
l.17
l.18
l.19
l.20
l.21
l.22
l.23
l.24
l.25
l.26
l.27
l.28
l.29
l.30
l.31
l.32
l.33
l.34
l.35
l.36
l.37
l.38
l.39
l.40
l.41
l.42
l.43
l.44
l.45
l.46
l.47
l.48
l.49
l.50
l.51
l.52
l.53
l.54
l.55
l.56
l.57
l.58
l.59
l.60
l.61
l.62
l.63

 BEGIN_INFO
   #
   # this is a sample Band-XCRYSDEN-Structure-File=20
   # aimed for Visualization of Fermi Surface=20
   #
   # Case:      just an example
   #
   # Launch as: xcrysden --bxsf example.bxsf
   #
   Fermi Energy: 0.83511
 END_INFO

 BEGIN_BLOCK_BANDGRID_3D
   here_we_have_some_examples
   BEGIN_BANDGRID_3D_simple_example
     2
     4 4 4
     0.0 0.0 0.0
     1.0 0.0 0.0
     0.0 1.0 0.0
     0.0 0.0 1.0
   BAND:  3
       0.000  0.192  0.385  0.577=20
       0.192  0.272  0.430  0.609=20
       0.385  0.430  0.544  0.694=20
       0.577  0.609  0.694  0.816=20
      =20
       0.192  0.272  0.430  0.609=20
       0.272  0.333  0.471  0.638=20
       0.430  0.471  0.577  0.720=20
       0.609  0.638  0.720  0.839=20
      =20
       0.385  0.430  0.544  0.694=20
       0.430  0.471  0.577  0.720=20
       0.544  0.577  0.667  0.793=20
       0.694  0.720  0.793  0.903=20
      =20
       0.577  0.609  0.694  0.816=20
       0.609  0.638  0.720  0.839=20
       0.694  0.720  0.793  0.903=20
       0.816  0.839  0.903  1.000=20
   BAND:  4
       1.000  0.942  0.885  0.827=20
       0.942  0.918  0.871  0.817=20
       0.885  0.871  0.837  0.792=20
       0.827  0.817  0.792  0.755=20
  =20
       0.942  0.918  0.871  0.817=20
       0.918  0.900  0.859  0.809=20
       0.871  0.859  0.827  0.784=20
       0.817  0.809  0.784  0.748=20
  =20
       0.885  0.871  0.837  0.792=20
       0.871  0.859  0.827  0.784=20
       0.837  0.827  0.800  0.762=20
       0.792  0.784  0.762  0.729=20
  =20
       0.827  0.817  0.792  0.755=20
       0.817  0.809  0.784  0.748=20
       0.792  0.784  0.762  0.729=20
       0.755  0.748  0.729  0.700    =20
   END_BANDGRID_3D
 END_BLOCK_BANDGRID_3D
                   =20

Legend:
l.01	beginning of INFO=20 section
l.02-09	a hash "#" character stands for = comment
l.10	a "`Fermi Energy:`" = string is=20 a marker for reading the value of Fermi = energy
l.11	end of INFO = section

l.13	beginning of 3D block of=20 bandgrids
l.14	one word comment - used as an = identifier=20 for this block
l.15	beginning of the 3D = bandgrid
l.16	number of bands in the=20 bandgrid
l.17	number of data-points in each = direction=20 (i.e. `nx ny nz` for 3D = grids)
l.18	origin of the = bandgrid Warning:=20 origin should be (0,0,0) (i.e. Gamma = point)
l.19	first spanning vector of the = bandgrid=20 (i.e. first reciprocal lattice = vector)
l.20	second spanning = vector
l.21	third spanning = vector
l.22	beginning of the BAND with = label=20 3
l.23-41	4x4x4 values in = row-major=20 mode
l.42	beginning of the BAND with = label=20 4
l.43-61	4x4x4 values in = row-major=20 mode
l.62	end of the = bandgrid
l.63	end of 3D bandgrid=20 = block