[Pw_forum] Clarification of celldm(4) in monoclinic

[Giovanni Cantele]

cos(ab) means cosine of the angle between lattice AXIS a and lattice AXIS b, so xcrysden gives you the correct view

see also Doc/INPUT_PW.txt at the description of the variable A, B, C, cosAB, cosAC, cosBC

Giovanni

> On 21 Dec 2015, at 12:16, Ridwan Agbaoye <agbaoyeridwan at yahoo.com> wrote:
> 
> Good day everyone 
> I need some help with clarification on celldm(4)=cos(ab) 
> 
> Does cos(ab) mean the cosine of angle between lattice parameter a and b 
> or it means the cosine of the product of the lattice parameter a and b that is cosine(lattice parameter a*lattice parameter b)
> 
> when i view my input file using xcrysden it looks like a cubic structure when i used celldm(4)=cos(ab)=0 since angle between a and b is 90 degree
> 
> but looked like a monoclinic structure when i used cosine(lattice parameter a*lattice parameter b)
> 
> Am i getting the cos(ab) wrong
> 
> Many Thanks to everyone on this forum 
> 
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