Establishing water model and simulation pressure setup

[Jianbo]

Hello Prof. Dubbeldam,

1. I would like to use SPC/E water model in RASPA and I checked the TIP5P model mentioned in Example/Non-basics/MD_NPT_water.

However, the critical parameters given there of Tip5p water model doesn't match neither the experimental data of water vapour nor the simulation data^[1].

Could you tell me how to determine these parameters for SPC/E model?

2. If I want to simulate water adsorption at different relative humidity, the vale of 'ExternalPressure' should be calculated form the correponding saturated vapour pressure of SPC/E model or the experiment data?

Kind regards,
Jianbo

[1] Vega, C., & Abascal, J. L. (2011). Simulating water with rigid non-polarizable models: a general perspective. Physical Chemistry Chemical Physics, 13(44), 19663-19688.

[David Dubbeldam]

1) if you need to convert from fugacity to pressure (or when computing excess) adsorption, that look upon the critical parameter that you want to use, and add them tot he molecule definition.
2) You input the fugacity (directly related to the pressure). So for your system you need to compute the correct fugacity to input.

[Jianbo]

So if I want to obtain water adsorption isotherm, I should do the followings:

1. calculate different fugacity values with corresponding relative humidity values
2. input these calculated increasing fugacity using command 'ExternalPressure'
3. set the value of 'FugacityCoefficient' to 1 rather 0

Is this right?

Thanks in advance.
Jianbo

[dubbelda]

Yes, when FugacityCoefficient is set to 1.0, then ExternalPressure is the fugacity which you input.