VASP support site: Forums / Physics questions / Why is the unit cell changing in the output file

VASP support site

Main Menu

Home
Links
Forum
Members
Stats
Upload
How to report bugs

Welcome

Online

Guests: 7
Members: 0
On this page: 1
Members: 6619, newest: atreyi_chem

Forums

VASP support site -> Forums -> Physics questions

<< Previous thread | Next thread >>

Why is the unit cell changing in the output file

Moderators: admin.

Author

Post

jaburt

Fri Aug 12 2005, 01:56PM

Registered Member #201
Joined Tue Jun 14 2005, 02:07PM
posts 3

I have been running geometry optimizations for certain minerals and there are descrepancies between the volume and direct lattice vectors from the input file and those given in the output file. Before any iterations are run the unit cell parameters (direct lattice vectors) in the output file are different from those given in the POSCAR file. At the end of the run the direct lattice vectors have not changed, but in the CONTCAR file I am given my original unit cell parameters. Does anyone why this is? Is VASP altering the volume of my unit cell before the geometry optimization?

Thanks

Jason

bruent

Mon Aug 15 2005, 08:14AM

Registered Member #301
Joined: Tue Jun 28 2005, 07:48AM
Location: Singapore
posts 13

May I see your OUTCAR and POSCAR?

Welcome to discuss with me via MSN

jaburt

Wed Aug 17 2005, 08:41PM

Registered Member #201
Joined: Tue Jun 14 2005, 02:07PM
posts 3

Here is the unit cell matrix from the OUTCAR file:

7.092920653 0.000000000 0.000000000
-2.158130545 7.511449542 0.000000000
-1.068749324 -0.306057406 5.433820096

Here is the unit cell matrix from the CONTCAR file (same as POSCAR):

7.1262000068047939 -0.0000000002506637 -0.0000000000675099
-2.1682563023359163 7.5466925965608587 -0.0000000002786286
-1.0737638010662385 -0.3074934000354140 5.4593150973523219

I know the difference isn't much, but why aren't they the same.

Date / Time

Counter

Today: 1470 (unique:400)
Ever: 1066629430 (unique:1065190962)
Record: 476169 (unique:476167)