Initial commit of the AENET code.

#+AUTHOR: Nongnuch Artrith
#+TITLE: Input file format for structural fingerprint setups

* List of keywords

  All keywords are case insensitive, but currently have to occur in the
  given order.  Blank lines and lines starting with =!=, =#=, or =%= are
  ignored.

  - =descr= (optional) :: Short text that describes the structural
       fingerprint setup and possible reference citations.  Has to be
       terminated by "end descr".
  - =atom= (required) :: The chemical species (symbol) of the central
       atom whose environment is captured by the setup.
  - =env= (required) :: A list of all atomic species that may occur in the
                      environment of the central atom and are captured
                      by this setup.  No blank lines are allowed.
  - =rmin= (required) :: The minimal allowed distance between two atoms
       (in the distance unit used in the XSF files).  This value is used
       by the neighbor list.
  - =functions= (required) :: Type and parameters of the basis functions.
       The example below is for functions of type 'Behler2011', and the
       names of the various functions and parameters follows the
       original publication. No blank lines allowed.

* Input file template (atomtype.stp)

#+BEGIN_EXAMPLE
DESCR
  short desscription and reference
END DESCR

ATOM <atom type>

ENV  <N>
<T_1>
<T_2>
...
<T_N>

RMIN <R>

FUNCTIONS type=<basis type>
<NF>
<parameters of function 1>
<parameters of function 2>
...
<parameters of function NF>
#+END_EXAMPLE

* Input file example (Ti.fingerprint.stp)

#+BEGIN_EXAMPLE
DESCR
  Structural fingerprint setup for Ti in bulk TiO2.
  Ref.: N. Artrith and A. Urban,
        Comput. Mater. Sci. 114 (2016) 135-150.
END DESCR

ATOM Ti

ENV  2
Ti
O

RMIN 0.75d0

FUNCTIONS type=Behler2011
70
G=2 type2=O  eta=0.003214 Rs=0.0000 Rc=6.5
G=2 type2=Ti eta=0.003214 Rs=0.0000 Rc=6.5
...
G=4 type2=O type3=O  eta=0.000357 lambda=-1.0 zeta=1.0 Rc=6.5
G=4 type2=O type3=Ti eta=0.000357 lambda=-1.0 zeta=1.0 Rc=6.5
...
#+END_EXAMPLE