In principle you should first determine the value of a for which your tube has no interaction with other images, just by making a scf calculation with fixed atomic geometry and fixed c, for different values of a (check variations in the total energy as a function of a). Then, you optimize c/a either by performing a variable-cell calculation, or by relaxing your system for different values of c/a and finding c/a that gives you minimum energy.
Marcos On Thu, May 6, 2010 at 6:55 PM, Erkan Tetik <[email protected]> wrote: > hello, > Thanks for your reply, I think, I understand that you want to tell me. In > this case, I have to optimise the 'a' and also 'c/a' variables and I need > to know; > For example a=b=9.6448 and c=4.2699(I obtained the tubegen), I will use > the large values for a variables. > > Best Regards. > Erkan Tetik > > > >
