crystal symmetry

[apple]

hi,
I am confused about two lattice types listed in my OUTCAR file when performing simple optimization.
I get the following message:

============================
LATTYP: Found a simple monoclinic cell.
ALAT = 5.6160778470
B/A-ratio = 0.8791697070
C/A-ratio = 2.7189498063
COS(beta) = -0.5705551425

Lattice vectors:

A1 = ( 1.4035875445, -0.0000032229, -5.4378554954)
A2 = ( -0.0000273284, -4.9374855153, -0.0000107338)
A3 = ( -14.3199295447, -0.0000688885, 5.3016451527)
Subroutine PRICEL returns following result:

LATTYP: Found a triclinic cell.
ALAT = 6.9143096256
B/A-ratio = 1.8499548214
C/A-ratio = 0.7140966753
COS(alpha) = 0.0000119398
COS(beta) = 0.3570588556
COS(gamma) = 0.8449755946

Lattice vectors:

A1 = ( -6.4581859600, -2.4687795885, -0.0681105519)
A2 = ( -11.5127570472, -0.0000768846, -5.5740658655)
A3 = ( -0.0000273284, -4.9374855153, -0.0000107338)

2 primitive cells build up your supercell.


Analysis of symmetry for initial positions (statically):

Routine SETGRP: Setting up the symmetry group for a
simple monoclinic supercell.


Subroutine GETGRP returns: Found 2 space group operations
(whereof 2 operations were pure point group operations)
out of a pool of 4 trial point group operations.


The static configuration has the point symmetry S_2 .

Analysis of symmetry for dynamics (positions and initial velocities):

Subroutine DYNSYM returns: Found 2 space group operations
(whereof 2 operations were pure point group operations)
out of a pool of 2 trial space group operations
(whereof 2 operations were pure point group operations)
and found also 2 'primitive' translations


The dynamic configuration has the point symmetry S_2 .
=====================================

So, is my structure monoclinic or triclinic? Why are two structures listed?
Thanks.

[tlchan]

The unit cell is monoclinic. VASP also checks if the unit cell can be obtained by smaller primitive cell using the subroutine PRICEL. For your case, VASP found such a primitive cell, but it corresponds to a triclinic structure.

[apple]

Thank you for the reply.