We know there are two methods which can deal with long-range Coulombic interactions, ewald and pppm. But I donit know how to choose them. I know the pppm method is faster than ewald method, so the pppm method usually is the first choice. But when we must choose ewald method, for example, the the system only a few ions or there is a strong external electric field ? is there some limits with the pppm method?
Any suggeston or recommending me some detailed papers which talk about their faults and advantages ?
Thanks in advance