2pi/SCALE, what is the meaning of SCALE?

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sigi14 · #1 Post by **sigi14** » Thu Nov 15, 2007 8:29 pm

Dear VASP users:

In the OUTCAR file the k-points are reported in cartersian or reciprocal coordiantes. The units for cartesian coordinates are 2pi/SCALE. But, what is SCALE? In the manual, for a face centered cubic lattice, SCALE = a (a being the lattice constant), which I understand; but I was wondering if "SCALE=a" in all the cases, or does it (SCALE) vary from lattice to lattice?

k-points in units of 2pi/SCALE and weight: k-points along high symmetry lines
0.07173830 0.08398421 0.04227440 0.050
0.07062719 0.08398421 0.04227440 0.050

k-points in reciprocal lattice and weights: k-points along high symmetry lines
0.58098697 0.49999999 -0.04888600 0.050
0.57198841 0.49999999 -0.04345422 0.050

Thanks for your help,
Sigi

#2 Post by **admin** » Fri Nov 16, 2007 2:38 pm

yes, of course, it is the corresponding lattice constant.

sigi14 · #3 Post by **sigi14** » Fri Nov 16, 2007 4:11 pm

[quote="admin"]yes, of course, it is the corresponding lattice constant.
[/quote]

Thank you for your prompt response (head-admin); but I was wondering is the SCALE variable is always equal to the lattice constant "a". In fcc all the sides have the same dimensions a=a=a and alpha=beta=gamma=90 degrees. But what if you have a crystalline structure where "a" not equal to "b" not equal to "c"; and alpha=gamma=90 but beta=124.4. Is the variable SCALE equal to "a" in this case, as well? Also, I think that "a" is giving in Ang.

Thanks for your help,
Sigi