[Wien] Formula to calculate lattice constant from cubic volume

[Kurt Lejaeghere]

Dear Naseem

this formula is only valid for fcc lattices when the volume is  
expressed in bohr^3 and when you want the lattice constant in angstrom.

In that case, there are 4 atoms in the conventional unit cell, so the  
conventional unit cell has a volume of 4 times that of the primitive  
1-atom unit cell (which is used in WIEN2k) (see for example  
http://people.seas.harvard.edu/~jones/ap216/lectures/ls_2/ls2_u7/sse_tut_1/solid1.html fig. 1.2.2, with the red cell conventional and the white one primitive). The fcc lattice vector is the third power root of the volume of the conventional unit cell (because this cell is cubic, and for a cube V = a^3). The factor 0.529177 then serves to scale the dimensions from bohr to  
angstrom.

Kind regards

Kurt

Citeren Naseem Hassan <raheskoon at gmail.com>:

> Dear Members
>
> I saw a formula to calculate lattice constant from cubic volume but was not
> able to locate its reference or derivation. The formula is
>
> Lattice constant = 0.529116(4×volume)^0.3333
>
> I know it might be easiest question to be asked here at this level but
> unfortunately could not find derivation. How you guys will encourage.
> Thank you