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["Wu Rongqin" <g0203654@nus.edu.sg>]

DEAR chUN Li

 

 

 

 

 

I have some basic questions about the input variables:

 

1)       Is there certain physics meaning about acell? Many examples use the value of the crystal constant. However, if there are two crystal constants (a and c), which one should we use?

Acell:     acell1(a), acell2(b), acell3(c)  this is the format.

 

2)       If I have defined the xcart, Must I also provide xangst, acell, and rprim?

 

Xcart,xangst and xred define the atomic coordinates, either one works. No need to imput all

And should the origin of the coordinates I defined be the same as the origin of the primitive vectors?

                               

No need. But if consistent, it more clear

 

That is, should the values of xcart be relative with the values of rprim (if rprim should also be defined)? I almost confused about the following variables: xcart, xangst, xred, acell, rprim, and rprimd.

                               

 

In simple words, the first three give out the atom coordinates in the cell, acell defines the three lattice constant. rprim and pprimd define the lattice type

3)        

4)       If the crystal is composed of two kinds of atom, I want to define a unit cell containing 20 atoms, then how can I setup the periodical boundary conditions to perform simulations? I have not found relative example in the tutorial.

 

 

You can set up your cell with any number atoms as you like!. Your cell will be expanded infinitely according to the lattice vectors. So the pbc is not a problem.