Dear lammps users,

I need to use fcm(ID,dim) function calculate the pressure of a section of my box. As a simple check I did a sample job and calculated fcm(all, x), fcm(all,y), and fcm(all,z). Then divided them by the cross section area. However, the value (after unit conversions) is not equal to pxx, pyy, and pzz. Is there a second term that I have to add to it to get the pressure of the box ( like NkT/V or sigma(mi vi vj)/V )? A sample of numbers I get is as below:

pxx(atm) pyy(atm) pzz(atm) fx(kcal/mol.Ang) fy(kcal/mol.Ang) fz(kcal/mol.Ang)

246.16825 478.012 209.28018 3.93e-13 -5.14e-13 3.07e-13

after unit conversions for 500 propane in a box of (45.7 Ang)^3

pxx(J/m3) pyy(J/m3) pzz(J/m3) fx((J/m3) fy(J/m3) fz(J/m3)

0.002429 0.0047176 0.002065 0.0006447 -0.000846 0.0005047

Thank you very much

Amir