atom position in triclinic region, in data file

LAMMPS LAMMPS Mailing List Mirror
1

I have a confusion about what the atom positions really are, in a data file with tilt.
Are the atom positions AFTER the tilt or BEFORE the tilt? someone please clarify this, thanks a lot.

If I use “read_data” to read a data file with non-zero tilt, like below a unit cube with tilt xy=0.2.
If I have only one atom, and I want it to be at the center of the tilted cube, then

should I write its coordinates still like (0.5, 0.5, 0.5) as below?
OR
should I write (0.6, 0.5, 0.5) instead? since my edge vectors after the tilt are A=(1, 0, 0), B=(0.2, 1, 0) and C=(0, 0, 1).
(the 0.6 comes from 0.5 plus half of 0.2)

2

I have a confusion about what the atom positions really are, in a data file with tilt.
Are the atom positions AFTER the tilt or BEFORE the tilt? someone please clarify this, thanks a lot.

First of all, this question can extremely easily verified empirically.
You already gave an example, why not try it out for real?

Second, read_data takes absolute coordinates, not scaled ones.

Axel.

3

And the data file should specify atom coords with the tilt.
In other words, the actual positions of the atoms. The
xlo, etc commands simply put a box around the atoms.

Steve

4

Thanks Axel, Steve. It seems the atom positions should be modified accordingly, to be consistent with the tilted box.