[Pw_forum] CO and N2 Crystals
amos at errno.com
Sun May 6 22:03:42 CEST 2007
My thanks for such a rapid reply especially on Sunday!
I will look at the download as soon as possible.
P.S. I enjoyed your video courses.
Nicola Marzari wrote:
> Dear Amos,
> ibrav specifies the 3-dimensional repetition pattern (i.e. the Bravais
> lattice) that you apply to the individual atoms you specify.
> E.g., an infinite fcc crystal of Al can be described as one Al atom
> repeated according to the translational symmetry of a fcc Bravais
> lattive, or as 4 atoms repeated in a simple cubic Bravais
> lattice, or in many other ways. One atom repeated fcc is the least
> expensive approach.
> A crystal of CO would typically have 2 atoms specified, and the
> ibrav of the crystal you think CO has. Of course molecular crystals can
> have unit cells that contain more than one inequivalent molecule - so
> you would have to specify more than 2 atoms. An isolated CO molecule
> would be described by a crystal with a lattice parameter large enought
> where the CO - CO interactions have become negligible.
> Having said this, this is a question that is not appropriate to the
> forum - it's really about crystals et al. Ashcroft Mermin chap 4-7 could
> be a good start, or the material in
> Amos Leffler wrote:
>> Dear Forum,
>> I would like to calculate the properties of the CO and N2
>> structures. Example03 calculates the scf for CO but does nothing
>> about the crystal. The problem is whether to use ibrav=0 to place
>> each atom or to use CO units with ibrav=2. Little is said in the
>> Users Guide about either of these approaches and I have looked at
>> some of Forum records but haven't found anything about either of
>> these methods. Hopefully someone can point me to references or
>> suggestions. There appears to be nothing about using polyatom
>> elements for crystalline structure but this would be a very useful
>> ability since there are many cases where it could be applied.
>> Amos Leffler
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
More information about the users