Small Possible Discrepancies

[GregorLauter]

Hi again,

I’ve come across two small possible discrepancies that I wanted to bring to your attention:

1. In the DREIDING and UFF data, H_h2 seems to have no LJ parameters, while H_com is assigned 10.0000 and 2.72000. Shouldn’t this be the other way around? In the referenced paper (Q. Yang., and C. Zhong, J. Phys. Chem. B 2005, 109, 24, 11862–11864
   , see below), they discuss two-site LJ parameters for hydrogen (and in other DREIDING and UFF data the situation for N₂ and O₂ is also reversed?)

"....Therefore, we refitted the two-site LJ parameters for hydrogen
based on fitting the PVT curve of bulk hydrogen (Vargaftik, N.B. Tables of Thermophysical
Properties of Liquids and Gases, John Wiley & Sons: New York, 1975). The LJ parameters obtained
are σ HH =0.272 nm and k HH ε / =10.00 K with hydrogen bond length of 0.074 nm..."

2. In the SO2.def file, shouldn’t the bonds be 0-1 and 0-2, since S is indexed as 0 (instead of 0-1 and 1-2 here)?

0 S_so2 0.86190 0.00000 0.00000
1 O_so2 1.72390 0.50700 0.00000
2 O_so2 0.00000 0.50700 0.00000

0 1 RIGID_BOND
1 2 RIGID_BOND

Best wishes,
Gregor

[lipelopesoliveira]

Hello Gregor,

Thank you for catching these errors.

You're absolutely right about the H2 parameters. The current model is actually incorrect, as it includes electrostatic interactions that weren’t considered in the referenced paper. I now realize that this model isn’t ideal for H2 adsorption. A few months ago, I ran a benchmark test and identified a more accurate model, particularly for low temperatures.

As soon as I have the time, I’ll update the parameters and include the benchmark results in the discussion section of this repository.

Regarding the SO2 bonds, you're correct—they should be 0-1 and 0-2. I’ll correct that as well.

I really appreciate the thorough analysis you’ve done on the data.

I'll keep this issue open until I fix the H2 parameters.

Best regards,
Felipe