Dear Steve,

I have a quick question.

In LJ units, all the quantities are printed out in (per units) in the log file. So, when we calculate any quantity by a compute and reduce it as a sum using reduce style, we get the per unit quantity. Here I was hoping that reduce style sums up the array and divides up with the no of elements in the array. However, when I am calculating a quantity for a group ( which is part of the system), it is dividing the summation by total no of atoms instead of no. of atoms in the group. Is it intended this way? I will put my example to clarify the situation better.

I was printing out the Szz component of the stress for my system. I was also printing out the values of Szz in the dump file for some other calculations for all atoms. I summed up the stress from the dump file for a snapshot in order to observe this behavior.

Summation of Szz for whole system is -2168 (over 18610 atoms). So average stress ( in energy units) should be ~ -0.1165. I am getting this correct in the log file. However for a group that I am interested in, the summation of Szz is -4785 (over 2160 atoms). So, average stress for group temp should be -4785/2160 = -2.21. However, in the output I am getting -4875/18610 = -0.26. Here, I tried compute reduce command two ways

#1.

compute str all stress/atom

compute savg temp reduce sum c_str[3]

#2

compute str temp stress/atom

compute savg temp reduce sum c_str[3]

I got the same output ( in the log file) both times.

Please advice.

Regards,

Vikas