Ray,
I started running the patched reaxc code on some more complex simulations (amorphous carbon instead of diamond) and found that the sum per-atom stress (divided by the volume) is not equal to the negative pressure. For some reason in the case of pure diamond they give the same number, but for an amorphous structure the numbers are vastly different. I checked with the old unpached reaxc code and the pressure and the sum per-atom stresses are the same. The old unpatched reaxc code gives consistent values for the pressure and summed per-atom stresses in both cases.
There aren’t any stress concentrations near the boundaries any more though. I’m not sure which is accurate, the pressure or the summed per-atoms stresses
I’ve attached a small example script that reproduces the error.
Thanks.
-Ben
NEW PATCHED REAX/C
Step Pxx staxx Pyy stayy Pzz stazz Pxy staxy Pxz staxz Pyz stayz
0 46413.308 -94306.389 166365.5 -210647.95 116817.53 -166782.1 -17682.294 25759.054 -12312.173 3709.1516 8750.2419 -12865.215
1 48648.007 -95202.808 162176.83 -206081.62 111729.42 -159333.24 -16306.786 21297.995 -9333.1294 4003.1086 10580.271 -14786.257
2 48374.373 -92606.51 149356.72 -191835.96 98832.929 -141329.87 -12193.038 10859.075 -4736.2656 6730.7258 14323.62 -18085.566
UNPATCHED REAX/C
Step Pxx staxx Pyy stayy Pzz stazz Pxy staxy Pxz staxz Pyz stayz
0 46413.308 -46413.308 166365.5 -166365.5 116817.53 -116817.53 -17682.294 17682.294 -12312.173 12312.173 8750.2419 -8750.2419
1 48648.007 -48648.007 162176.83 -162176.83 111729.42 -111729.42 -16306.786 16306.786 -9333.1294 9333.1294 10580.271 -10580.271
2 48374.373 -48374.373 149356.72 -149356.72 98832.929 -98832.929 -12193.038 12193.038 -4736.2656 4736.2656 14323.62 -14323.62
Ben Jensen
PhD candidate
Mechanical Engineering - Engineering Mechanics
Michigan Technological University
Houghton, MI
reaxc_stress_error2.zip (20.2 KB)