The ABINIT Users Mailing List ( CLOSED )

[Xavier Gonze <gonze@pcpm.ucl.ac.be>]

On 24 May 2007, at 10:43, andrea.bordoni@unimi.it wrote:

> Hi,
> I'm trying to write an input file to compute the total energy for  
> different geometries for the same "molecule".
> For example, consider three atom, and you want to change the  
> distances between two of them and the third atom independently.
> I was trying to do it with a double loop on the positions of the  
> atoms, using as loop parameter xangst or xcart.
> But it is possible to do a double loop in which there is one single  
> parameter changing in two different ways?

Dear Andrea,

It is not possible to use xangst (or xcart) to make part of it vary  
with the first
index of the double loop, and some part of it to vary with the second  
index of the double loop.

However, there is a little-known feature of ABINIT that will likely  
do the work if two of your
atoms are identical, namely, the capability
to define groups of atoms, and to translate them, with input  
variables that are independent
of xangst and xcart. These groups of atoms are called "object".  
Please, see the
definition of the nobj variable :
http://www.abinit.org/Infos_v5.3/input_variables/vargeo.html#nobj .
You should be able to make the input variable objatr vary with one  
index,
and xangst (or xcart) vary with the second index.

Good continuation,
Xavier