I met some questions about ewald.cpp. Firstly, when we use gaussian charge distribution, the short range force has a form of erfc function. And in the ewald.cpp, we try to use extract(‘cut_coul’, itmp) to get a cut-off radius. But how do we calculate the short range term in real space.

Secondly, I am confused about the virial calculation per atom ug[k]*vg[k][j]*partial_peratom. How does this formula comes. Is there any reference.