RKmax is a very importat parameter for any WIEN2k calculation. Is this compulsory to do the same calculation for various RKmax values to confirm its suitable value fro the material? Or a good guess is enough?
It is not compulsory, but how do you check that your RKmax parameter is optimized?
On the one hand, a high RKmax value will give you precision but you will need far more computational effort. On the other hand, a low RKmax value will be fast but your results will not be reliable.