My Community

<span class='smallblacktext'>[ Edited ]</span>

<span class='smallblacktext'>[ Edited Fri Dec 11 2009, 05:24AM ]</span>

sorry, you seem to mix up the files of several runs, the data you show are not consistent with the files.

1) The CONTCAR you show cannot be the CONTCAR of an ISIF=2 run,
with the POSCAR you given, because obviously the volume has been relaxed. please check OUTCAR of that run. ISIF=2 keps the cell volume and shape constant

2) the positions in the nearest neighbors table are given in direct (not in carthesian) coordinates, but again you seem to have started from a different POSCAR this time

I apologize for mixing a couple of runs. I am using ISIF=2. I’m examining nanotubes, but after relaxing the structure, I’m left with something that looks nothing like a nanotube. I don’t know, it seems that VASP is reading some of the information in a way I don’t just can’t follow. Here is my POSCAR (the first part):

Carbon Nanotube
1.0
10 0 0
0 10 0
0 0 4.26739
40
Cartesian
3.929290 0.000000 -0.712694
3.929290 0.000000 -2.133694
3.736976 1.214217 1.421000
3.736976 1.214217 0.000000

Of course, the nearest neighbor table is in direct cords:

ion position nearest neighbor table
1 0.393 0.000 0.833- 4 1.42 40 1.42 2 1.42
2 0.393 0.000 0.500- 1 1.42 3 1.42 39 1.42
3 0.374 0.121 0.333- 4 1.42 6 1.42 2 1.42
4 0.374 0.121 0.000- 5 1.42 1 1.42 3 1.42

The first two cords make sense: it’s the Cartesian coords divided by the lattice vector in that direction, but I don’t know how they get .833-. It is also putting a negative sign behind every number in that fourth column (the one with .883-) even though not all of the z coordinates are negative. I just have no idea what it's doing or what I am doing wrong

For your first atom, the z-coordinate is -0.71 A. Since the system is periodic along the z direction, the coordinate can be uniformly translated along the z-direction by the lattice vector. Therefore, it is equivalent to say that the z-coordinate of the atom is 3.55 A. In direct coordinate, it will be 0.833.

The "-" is not a negative sign. It is a dash. After the dash, vasp prints out the number of the nearest neighbors of the atom, and their distance away from that atom.