[Pw_forum] about lattice basis vectors?

[Tone Kokalj]

On Tue, 2008-04-22 at 10:30 +0800, Fan Yang wrote:
> 
> Thanks for stefano's reply, and I'm also confused the "lattice
> specification" in PWGUI, which could be descripted either by celldm()
> or by A,B,C,cosAB,cosAC,cosBC, but not both. 

Which is ok. It's like walking or driving a car: can't do both at the
same time.

> If the former method is selected, there has no problem. However, if I
> use the latter, the structure could not be displayed properly in
> XCrySDen. It seems that the angles between vector A and B, A and C, B
> and C are defined as alpha, beta, and gamma respectively, which is
> different from the widely-used definition (the angles between vector B
> and C, A and C, A and B are defined as alpha, beta, and gamma
> respectively). There may be a small bug about specifying lattice,
> either in PWscf or in XCrySDen.

You are right. Thanks! There was a typo in xcrysden's pw.x-input to xsf
filter, i.e.:

         celldm(1) = a / bohr
         celldm(2) = b / a
         celldm(3) = c / a
         celldm(4) = cosab
         celldm(5) = cosac
         celldm(6) = cosbc 

Of course it should be:

         celldm(1) = a / bohr
         celldm(2) = b / a
         celldm(3) = c / a
         celldm(4) = cosbc
         celldm(5) = cosac
         celldm(6) = cosab

You may use the celldm() for the time being to display the structure.

Regards, Tone

-- 
Tone Kokalj <tone.kokalj at ijs.si>
J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia (tel:
+386-1-477-3523 // fax:+386-1-477-3822)