Basis set problem

[Tian]

Dear Vaspers,
I am doing 1D polymer calculations. I am wondering if the size of the box (unit cell) can affect the basis set size for the same ENCUT. For example, the two boxes are 10*10*3 and 20*20*3, the ENCUT are both 400eV. Dose it mean the basis set is more complete for the later than the former.

The reason I ask is that my system is a kind of charged polymer with helical geometry, and I want to optimized the geometry to get the helical pitch. When I changed the size the box, I got different very different pitch values. Also, I noticed that the optimized helical pitch is highly dependent on the ENCUT I used.

Thank you!!

[admin]

for a fully covberged basis set, it should not affect the results if you increase the unit cell size further.
--) please be aware of the effects when you charge a periodically repeated polymer!