Solubility parameter for water

Hi,


I have used the Amorphous Cell module for determination of the solubility parameters, and it works well, I think.

But, for some materials of which electrostatic interaction is dominant, I've got some strange results.


I thought that total solubility parameter should be equal to the square root of (δ_vdW ^2 + δ_es ^2), and in most cases it is right.

For water, however, they are not the same; see below.


-------------------

1) ethanol


   Average         Std. Dev.

   -------         ---------
Cohesive Energy Density (J/m^3) : 3.62634e+008 1.6965e+007
Solubility Parameter ((J/cm^3)^0.5) :      19.0377     0.446644
- Electrostatic ((J/cm^3)^0.5) :      16.1661     0.461462
- van der Waals ((J/cm^3)^0.5) :       10.034     0.628692

2) n-hexane

    Average     Std. Dev.
    -------     ---------
Cohesive Energy Density (J/m^3) : 2.20625e+008 2.60362e+006
Solubility Parameter ((J/cm^3)^0.5) :      14.8532    0.0876968
- Electrostatic ((J/cm^3)^0.5) :     0.472532    0.0798629
- van der Waals ((J/cm^3)^0.5) :      14.8454    0.0876796

3) water


    Average     Std. Dev.

    -------     ---------

Cohesive Energy Density (J/m^3) : 1.84406e+009 1.81845e+008

Solubility Parameter ((J/cm^3)^0.5) :      42.8885      2.15347

- Electrostatic ((J/cm^3)^0.5) :      47.9448      2.54832

- van der Waals ((J/cm^3)^0.5) :            0            0


---------------------------



How to understand the result above?

And why it occurs?



Thanks,

Kunsil