I simulated the thermodynamic properties of 612 TIP3P water model. Here is the input file when I run production MD.
&cntrl
imin=0,irest=1,ntx=7,
ntb=2,pres0=1.0,ntp=1,taup=2.0,
cut=10.0,ntr=0,ntc=2,ntf=2,
tempi=300.0,temp0=300.0,
ntt=3,gamma_ln=4.0,
nstlim=1000000,dt=0.002,
ntpr=100,ntwx=100,ntwr=1000
/
I have calculated some properties :the Isobaric heat capacity is 18.24(kcal/mol), the Isothermal compressibility is 93(10^-6/atm), the thermal expansion coefficient is 81(10^-5/k). It is these three results that confused me. Please tell me are they reasonable?
Thank you
At 2011-07-18 17:02:01£¬steinbrt.rci.rutgers.edu wrote:
>Hi,
>
>> I used TIP3P water model to simulate some properties for liquid water at
>> 300k and 1atm.The result are based on averages covering 2ns.But the
>> thermodynamic results, for example the isothermal compressibilities and
>> isobaric heat capacity, are different from the calculated properties
>
>Did you exactly replicate the simulations in your reference paper? Changes
>in simulation length, cutoffs, electrostatics model, time-steps, etc. can
>strongly influence your results. You do not give details about your
>simulations and do not say how big the differences are that you see, so
>its hard to judge if the results are reasonable.
>
>Note that MD simulations (especially long ones) are not exactly
>replicable. Due to round-off differences, trajectories diverge and you may
>see slightly different results when running even the same simulation setup
>twice.
>
>> pointed by some paper using the same TIP3P water model .Please tell me
>> what is the actual result or the range of the properties.
>
>Im not sure there is an 'actual' result, the behaviour of a water model
>will depend on the physical parameters used in the simulation.
>
>Kind Regards,
>
>Dr. Thomas Steinbrecher
>formerly at the
>BioMaps Institute
>Rutgers University
>610 Taylor Rd.
>Piscataway, NJ 08854
>
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Received on Mon Jul 18 2011 - 07:30:03 PDT
