stress output problem

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1

Hi, everyone:

I am dealing with steady shear of polymer blends use fix/form command and DPD thermostat. If got a DPD thermostat then the fix/sllod cannot be used (am I right ?) which brings the troubles e.g. the temp/deform is not correct to dump the system temperature under high rate. I used the temp/profile to obtain the real temperature. However I am quite doubt whether the flow kinetic components are correctly excluded when compute the system pressure and stress tensors following the “compute press all pressure mytemp”, though it seems the energy tensors have been dealt in the temperature compute command stated in the manual, considering this is not a fix/sllod condition.

Following is the main script for the Shear and Temperature & Pressure Computation.

/*~~~~~~~~~~~~~
thermo_style custom step temp cpu etotal pxx pyy pzz lx ly lz xy xz yz
thermo 100

2

You would not want to use pair dpd/tstat and fix nvt/sllod, b/c

you would then be thermostatting the system twice.

When you use compute pressure, you specify a temperature
compute to use for the kinetic components. If you use

compute temp/deform, then it will subtract out the flow velocity

(assuming it matches the deformation rate) correctly,

leaving the thermal KE components.

Steve

3

Dear Steve,

Thanks for you reply. In fact I want to know whether the temp/profile used in the pressure calculation will subtract out the flow velocity as in the temp/profile calculation.

Simon

4

If you specified the ID of a compute temp/profile
in the compute pressure command that you also
specified, then yes, it will use that “temperature”

to compute the pressure. The default pressure,
will, of course, not do that.

Steve