Multiple Thermostats

Hello,

I have a polymer adsorbed to a silica slab. A portion of the slab is fixed in place using “fix spring/self”. If I use “fix nvt all”, with the constrained atoms, my first thought is that it would skew the temperature. I’m thinking I should use two thermostats, one for the slab and one for the polymer…does that make sense?

What would be the proper way to have two thermostats? My first thought is to have two groups and two “fix nvt”:

“”""
group polymer # define group here
group silica # define group here

fix 1 polymer nvt temp 300.0 300.0 100.0
fix 2 silica nvt temp 300.0 300.0 100.0

compute 1_temp polymer temp
compute 2_temp silica temp
“”""

Is this correct?

Thanks for the help,
Alex

Hello,

I have a polymer adsorbed to a silica slab. A portion of the slab is fixed in place using “fix spring/self”. If I use “fix nvt all”, with the constrained atoms, my first thought is that it would skew the temperature. I’m thinking I should use two thermostats, one for the slab and one for the polymer…does that make sense?

not much. by the same token you could worry about atoms being connected with bonds and angles versus atoms that are not.
but why guess? you can easily measure whether there is a systematic difference by defining two temperature computes and monitor their values over time after the system has been suitably well equilibrated (and record a histogram of their temperature distributions and determine their average temperature).

axel.