[Pw_forum] ibrav for orthorhombic space group

[David Foster]

Hi everybody

Orthorhombic space group (Numbered from 16 to 74) has five different kinds of classes starting

with "P" "C"  "A"  "F"  "I".

P such as 56.Pccn	 or  57.Pbcm   

C such as 36.Cmc21  or   37.Ccc2

A such as 40.Ama2   or    41.Aba2

F such as 42.Fmm2	    or     43.Fdd2

I such as 44.Imm2	   or    45.Iba2    

My question is about ibrav assignment to above space groups.


in manual we have:

========================
 8          Orthorhombic P                  celldm(2)=b/a
                                             celldm(3)=c/a
      v1 = (a,0,0),  v2 = (0,b,0), v3 = (0,0,c)

  9          Orthorhombic base-centered(bco) celldm(2)=b/a
                                             celldm(3)=c/a
      v1 = (a/2, b/2,0),  v2 = (-a/2,b/2,0),  v3 = (0,0,c)
 -9          as 9, alternate description
      v1 = (a/2,-b/2,0),  v2 = (a/2,-b/2,0),  v3 = (0,0,c)

 10          Orthorhombic face-centered      celldm(2)=b/a
                                             celldm(3)=c/a
      v1 = (a/2,0,c/2),  v2 = (a/2,b/2,0),  v3 = (0,b/2,c/2)

 11          Orthorhombic body-centered      celldm(2)=b/a
                                             celldm(3)=c/a
      v1=(a/2,b/2,c/2),  v2=(-a/2,b/2,c/2),  v3=(-a/2,-b/2,c/2)
===========================

so, it is clear that ibrav for "P" is 8, for "I" is 11 (I am not sure), for "F" is 10.

What about "C" and "A"?

            


Regards

David Foster

Ph.D. Student of Chemistry