how to determine the proper cutoff distance?

[akareem28]

Hi Sir,
I am calculating the VP of binary liquids, how much distance do I need to consider as a cutoff distance.

[vorotis]

Hi akareem28,

A proper cutoff distance (Rc) depends on the arrangement of atoms. When Rc is larger than the threshold value of the system, the Voronoi polyhedra are properly constructed. So, you should start with a sufficiently large Rc. However, the computation time increases with Rc. So, you may want to decrease the value of Rc to reduce the computational cost. However, when Rc is smaller than the threshold value, the resultant polyhedra are not Voronoi polyhedra. This means that the polyhedra overlaps and do not tile the space. In this case, "Warning: rc_for_ca may be too small." is printed on the screen and you need to use a larger Rc.

In the example 04_binary, Rc is set to be 2.5 times the diameter of the larger atom. This might help you find a proper Rc for your problems.

Best regards,
Kengo Nishio