Re: langevinTemp and system temperature

From: Joshua Adelman (jadelman_at_berkeley.edu)
Date: Fri Jan 29 2010 - 09:42:19 CST

There is a finite relaxation time that is required for the Langevin Thermostat to equilibrate to a particular temperature. If you consider more than the first output after you change the langevinTemp parameter, does the system temperature approach the desired temperature?

Josh

On Jan 29, 2010, at 10:30 AM, snoze pa wrote:

> Dear NAMD users,
>
> I am trying to change the temperature in steps but something strange
> happening as can be seen in following output
> The "Setting parameter langevinTemp to 200" and the temp is 15.6240 !
> Any idea. I will highly appreciate your help.
>
> WRITING EXTENDED SYSTEM TO RESTART FILE AT STEP 115000
> WRITING COORDINATES TO DCD FILE AT STEP 115000
> WRITING COORDINATES TO RESTART FILE AT STEP 115000
> FINISHED WRITING RESTART COORDINATES
> WRITING VELOCITIES TO RESTART FILE AT STEP 115000
> FINISHED WRITING RESTART VELOCITIES
> TCL: Writing to files with basename heat_P.
> WRITING EXTENDED SYSTEM TO OUTPUT FILE AT STEP 115000
> WRITING COORDINATES TO OUTPUT FILE AT STEP 115000
> WRITING VELOCITIES TO OUTPUT FILE AT STEP 115000
> TCL: Setting parameter langevinTemp to 200
> TCL: Running for 5000 steps
> PRESSURE: 115000 -30091 -192.727 -13.3307 -209.937 -29953.4 33.3876
> -12.6291 7.78817 -29852.5
> GPRESSURE: 115000 -3129.63 -53.486 4.50735 -57.6072 -3156.02 51.9169
> 12.2991 0.849874 -3025.97
> ENERGY: 115000 79.6567 239.8201 419.1070
> 9.3616 -557285.8838 68203.1426 8.8448
> 0.0000 3726.6078 -484599.3432 15.6240
> -488325.9510 -484589.6426 15.6240 -29965.6279
> -3103.8758 1245387.7826 -29965.6279 -3103.8758
>
> Info: Initial time: 4 CPUs 0.25108 s/step 2.90602 days/ns 147.734 MB memory
> Info: Initial time: 4 CPUs 0.25109 s/step 2.90613 days/ns 147.731 MB memory
> Info: Initial time: 4 CPUs 0.250974 s/step 2.90479 days/ns 147.811 MB memory
> Info: Benchmark time: 4 CPUs 0.251096 s/step 2.9062 days/ns 147.812 MB memory
> Info: Benchmark time: 4 CPUs 0.251024 s/step 2.90537 days/ns 147.738 MB memory
> Info: Benchmark time: 4 CPUs 0.250939 s/step 2.90438 days/ns 147.78 MB memory
>
> Also at 300K
>
> WRITING EXTENDED SYSTEM TO RESTART FILE AT STEP 165000
> WRITING COORDINATES TO DCD FILE AT STEP 165000
> WRITING COORDINATES TO RESTART FILE AT STEP 165000
> FINISHED WRITING RESTART COORDINATES
> WRITING VELOCITIES TO RESTART FILE AT STEP 165000
> FINISHED WRITING RESTART VELOCITIES
> TCL: Writing to files with basename heat_P.
> WRITING EXTENDED SYSTEM TO OUTPUT FILE AT STEP 165000
> WRITING COORDINATES TO OUTPUT FILE AT STEP 165000
> WRITING VELOCITIES TO OUTPUT FILE AT STEP 165000
> TCL: Setting parameter langevinTemp to 300
> TCL: Running for 5000 steps
> PRESSURE: 165000 -30080.6 -175.244 -34.9534 -176.999 -29970.7 42.3602
> -34.1171 41.3638 -29833.6
> GPRESSURE: 165000 -3106.28 -49.7584 10.03 -47.0878 -3154.23 60.7936
> -0.837666 62.3958 -3026.63
> ENERGY: 165000 85.7171 246.8998 415.4260
> 9.5578 -557409.3785 68306.4849 8.9140
> 0.0000 3737.1702 -484599.2086 15.6683
> -488336.3788 -484589.4944 15.6683 -29961.6392
> -3095.7110 1245387.7826 -29961.6392 -3095.7110
>
> Info: Initial time: 4 CPUs 0.252959 s/step 2.92777 days/ns 147.785 MB memory
> Info: Initial time: 4 CPUs 0.253001 s/step 2.92826 days/ns 147.799 MB memory
> Info: Initial time: 4 CPUs 0.253004 s/step 2.92829 days/ns 147.836 MB memory
> Info: Benchmark time: 4 CPUs 0.252791 s/step 2.92582 days/ns 147.799 MB memory
> Info: Benchmark time: 4 CPUs 0.252604 s/step 2.92366 days/ns 147.798 MB memory
> Info: Benchmark time: 4 CPUs 0.252828 s/step 2.92625 days/ns 147.837 MB memory
>
>
> Somehow it is setting the langevinTemp to 300 but the temp remain
> 15.6683! which I never observed before.
>
>
> Thank you
>
> S
>

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