Hi all,
I want to calculate/output the value of total force for some water molecules in a specified region. Oxygen atoms were specified as groups OXY. Hydrogen atoms were specified as groups HYD.
This is the main body of my input file:
fix 2 all nvt temp 300.0 300.0 100.0
region region1 block INF INF INF INF 24.0 24.5 units box
variable oxy_in_region_1 equal count(OXY,region1)
variable hyd_in_region_1 equal count(HYD,region1)
variable force_1_o equal Fcm(OXY,z,region1)
variable force_1_h equal Fcm(HYD,z,region1)
thermo_style custom step temp epair pe etotal press vol v_force_1_o
thermo_modify flush yes
thermo 100
run 1000000
But I always got the error:
Step Temp E_pair PotEng TotEng Press Volume force_1_
ERROR: Invalid math/group/special function in variable formula
I supposed those variable settings were correct. Did I miss any important information in the manual?
Many thanks in advance!
Hang