# Is this a wright way to get the temperature when there is streaming velcocity in the group? And how can I get the temperature of two groups?

Dear Lammps users
I have explicit wall atoms at Z direction and they are defined as a group. There is another one group of atoms defined as flow. What I want to do is to create initial velocity for both wall and water, and then the wall is moved at constant velocity at X direction. To conduct the heat during the flow, I am going to apply langevin thermostat to the wall.I want to thermostat only the thermo temperature without affecting velocity which I assign to the wall, so the “compute temp/profile” command is used to subtract the center of mass velocity when wall temperature is thermostatted. Also, I want to calculate the temperature of flow. The flow will also move due to the move of the wall, but I do not thermostat the flow, so only “compute temp” command is used. Because the “compute temp” can automatically subtract the velocity biases (the velocity of the flow in X direction) when thermo temperature is calculated , so I think it is enough. The following commands are what I used in lammps.

#initial velocities for wall
compute solid_temperature wall temp
velocity wall create 300 8982954 temp solid_temperature
thermo_modify temp solid_temperature

#create the initial velocity of the wall and thermostat the wall
compute solid_temperature wall temp/profile 0 0 0 z 10
velocity wall create 300 8982954 temp solid_temperature
fix lng_solid_temperature wall langevin 300 300 0.5 123456
fix solid_flow all nve
thermo_modify temp solid_temperature

#Couette flow (apply the velocity to the wall)
velocity bot_wall set 0.0 0.0 0.0 units box
velocity top_wall set 0.7 0.0 0.0 units box

Am I using the correct command to achieve what I want?

Another question is how can I output the “flow_temperature” and “solid_temperature” separately?I used the “thermo” command, but only one “temp” is outputted, and I think it is “solid_temperature”.

Fan Li