Effect of ewald-rtol on accuracy of the PME calculation?

User discussions
1

Hi, is anyone aware of any (systematic) studies on the effect of ewald-rtol on accuracy (and performance) of the PME calculation?

I’ve seen some discussions on the old forum about ewald-rtol but I haven’t found any detailed testing.

From the 2018 manual:

ewald-rtol
The relative strength of the Ewald-shifted direct potential at rcoulomb is given by ewald-rtol. Decreasing this will give a more accurate direct sum, but then you need more wave vectors for the reciprocal sum.

Thanks,
Andrew DeYoung
Carnegie Mellon University

2

The effect of the different PME parameters on the accuracy is complex and they are all interlinked. Decreases ewald_rtol decreases the real-space error, which is directly given by this value, but increases the reciprocal space error when you keep the grid spacing and PME order fixed, as the PME beta parameter increases. The is literature that describes and analyzes all the errors, but it is somewhat complex.