[Pw_forum] Error in routine scale_h (1)

[Alexey Akimov]

Dear all,

I'm trying to optimize a relatively large system such as 2 C60 / unit cell. So i start with relatively large cell dimensions. I'm doing vc-relax calculations with either 'damp'&'damp-pr' or 'bfgs'&'bfgs' for ionic and cell dynamics options. However, after some number (~50-70) of successful  (ionic/cell) steps the calculations crash with the error: 

     Error in routine scale_h (1):
     Not enough space allocated for radial FFT: try restarting with a larger cell_factor.

It seems like this happens when the size of the simulation cell changes by some notable amount with respect to the starting one. Perhaps, the program automatically changes the plane wave basis set (increases). If i restart the calculations with the latest (most optimal) configuration of the system and the same amount of memory allocated, the further optimization can proceed some more time (also ~50 - 70 steps) before next crash. So in principle it is still possible to achieve the convergence with this sequence of operations, but it is quite inconvenient to reset the calculations every 50-70 steps. 

So my question: is there any way to avoid this and get optimized results without intermediate crashes (apart from increasing the amount of memory reserved in the beginning)? 

Thank you,
Alexey


-- 
Dr. Alexey V. Akimov

Postdoctoral Research Associate
Department of Chemistry
University of Rochester

aakimov at z.rochester.edu