[lammps-users] Lammps input for a skewed cell


I am a new lammps user having trouble lammps read my unit-cell! This is what it looks like :

a = {a, 0, 0}, b={a/2,a*sqrt(3)/2,0}, c={0,0,c}

I am not clear about the (xy,xz,yz) as defined in the manual i.e. is xy == yx? Given their definitions in terms of a,b,c and alpha,beta,gamma I entered this:

0 a xlo xhi
0 a*sqrt(3)/2 ylo yhi
0 c zlo zhi

a/2 0.0 0.0 xy xz yz

with the atom positions entered in cartesian coordinates. The resulting structure doesn't seem right (what is the best viewer? vmd crashes or shows a blank screen. ). I suspect lammps is looking for 'xy' while I want to enter my 'yx', but not sure. I am using the OCT-31/2010 release.

Is there a way to just enter {a,b,c,alpha,beta,gamma} directly or the full 3x3 rotation-matrix or read/convert from a .pdb or VASP-poscar file?

Thank you for any helpful response.