Hi everyone;
I'm traying to calculate the Hildebrand dispersion and polar solubility parameters of water (δ²=δd²+δp²) using forcite module, however, I always obtain a negative value (appear blank in the result table).
I used a cell containing 100 water molecules, with a density of 0.997g/cm3, and Ewald summation, the simulation was done in the NVT ensemble with 1000ps. the following table summarizes the results that I obtained:
Dreiding | CompassII | TIP3P | SPC/E | F3C | PCFF | Water (exp)* | ||||||||||
charge equilibration | Qeq | Qeq | Focrefield assigned | Focrefield assigned | Focrefield assigned | Focrefield assigned | Focrefield assigned | |||||||||
Solubility parameter | δ | δd | δ | δd | δ | δd | δ | δd | δ | δd | δ | δd | δ | δd | δ | δd |
(J/cm^3)^0.5 | 50.94 | n/a | 37.2 | n/a | 47.7 | n/a | 50.2 | 60.3 | 55.7 | n/a | 81.2 | n/a | 47.2 | 7.2 | 47.9 | 12.9 |
As you can see, no forcefield/model gives a good value of the dispersive solubility parameter, I also tried equilibrating in the NPT ensemble, and a simulation with higher time 9000ps, but δd is always n/a and the Van der Waals cohesive energy is always positive.
I don't understand why, any explanation/advice/suggestions/solution?
Thank you in advance!
JARRAY
*Barton A.F.M.Handbook of solubility and other cohesion parameters- 2nd ed. 1991.
