[AMBER] About the unit of the pressure in the md.out file?

From: ۡ <wangxianwei1228.163.com>
Date: Mon, 28 Oct 2019 15:35:14 +0800 (CST)

Hi all,


In the output file (.out) in Amber, there is the pressure (PRESS = ) :
 NSTEP = 500 TIME(PS) = 101.000 TEMP(K) = 302.34 PRESS = -752.0
 Etot = -63895.0158 EKtot = 15178.2163 EPtot = -79073.2321
 BOND = 416.0297 ANGLE = 1058.6524 DIHED = 1369.0819
 1-4 NB = 510.9558 1-4 EEL = 2505.0632 VDWAALS = 9509.7092
 EELEC = -94442.7242 EHBOND = 0.0000 RESTRAINT = 0.0000
 EKCMT = 6851.6580 VIRIAL = 11353.8350 VOLUME = 277273.8500
                                                    Density = 0.9056
 Ewald error estimate: 0.5781E-04
 ------------------------------------------------------------------------------
 
 
 NSTEP = 1000 TIME(PS) = 102.000 TEMP(K) = 300.94 PRESS = -612.6
 Etot = -64036.8038 EKtot = 15108.0303 EPtot = -79144.8341
 BOND = 439.8601 ANGLE = 1093.5015 DIHED = 1375.8586
 1-4 NB = 484.5553 1-4 EEL = 2499.9587 VDWAALS = 9348.5379
 EELEC = -94387.1062 EHBOND = 0.0000 RESTRAINT = 0.0000
 EKCMT = 6756.9737 VIRIAL = 10377.2016 VOLUME = 273707.5876
                                                    Density = 0.9174
 Ewald error estimate: 0.6824E-04
The reference pressure is set to 1.0 bar (pres0 = 1.0), while in the output file, the pressure is several hundred (e.g.PRESS = -752.0 and PRESS = -612.6).
Why is it negative and so large? What is it unit, bar?
I have searched online and Amber manuals, only find a brief description about thisNote that fluctuations in the instantaneous pressure on each step will appear to be large (several

hundred bar), but the average value over many steps should be close to the target pressure.. Does it mean that the pressure in the step (e.g. NSTEP = 500) of MD simulation
is -752.0 bar? What is the mean of the netagive sign? but I cann't confirm any clear definition yet. Please help me to clarify it.
Best,
Xianwei Wang
_______________________________________________
AMBER mailing list
AMBER.ambermd.org
http://lists.ambermd.org/mailman/listinfo/amber
Received on Mon Oct 28 2019 - 01:00:02 PDT
Custom Search