hi,
I am testing out a sodium chloride crystal with 8 atoms in a periodic box. When I run the simulation with just coloumb effects using a pppm long-range solver I get energies which are in agreement with the literature(eg. Kittel). However, I wanted to see if adding bond coeffs would affect anything. So I added one bond between an Na and a Cl with a large energy coefficient and the distance coeffient I set to equal their equilibrium distance of 2.82 Angstroms. The bond energy came out as zero which I expected but the coloumb energy changed. Am I missing something?
-Dan
My first run with no bonds:
PPPM initialization ...
G vector = 0.459197
grid = 32 32 32
RMS precision = 5.38115e-09
brick FFT buffer size/proc = 117649 32768 64827
Setting up run ...
Memory usage per processor = 9.41173 Mbytes
Step Temp PotEng E_mol E_long E_coul E_bond TotEng
0 0 -823.12432 0 -668.87741 -154.24691 0 -823.12432
100 1.8676036e-28 -823.12432 0 -668.87741 -154.24691 0 -823.12432
200 8.5587672e-28 -823.12432 0 -668.87741 -154.24691 0 -823.12432
The second run with one bond added:
PPPM initialization ...
G vector = 0.459197
grid = 32 32 32
RMS precision = 5.38115e-09
brick FFT buffer size/proc = 117649 32768 64827
Setting up run ...
Memory usage per processor = 9.48809 Mbytes
Step Temp PotEng E_mol E_long E_coul E_bond TotEng
0 0 226.17823 0 -668.87741 895.05564 0 226.17823
100 1.814077e-27 226.17823 0 -668.87741 895.05564 0 226.17823
200 1.1599017e-25 226.17823 0 -668.87741 895.05564 0 226.17823