[ghemical-devel] Tripos 5.2

[Rzepa, Henry]

>On Jul 27, 2006, at 2:36 AM, Tommi Hassinen wrote:
>
>>>Actually, what would be really nice is if the ghemical engine would substitute parameters from neighbors in the periodic table instead. So if I simulate Si and no parameters exist, it uses carbon but with a larger vdW radius. Same thing for Se using S parameters, etc.
>>
>>this would work pretty well for distances and radii, but I'm afraid it would be too inaccurate for angle and torsion terms.  :(
>
>You're telling me that it's more inaccurate than using hydrogen parameters? Yes, I agree that it's worse than having accurate parameters for a range of elements. But I don't see why it's bad for late-period elements of the same family -- better than nothing!


How about  UFF?

A. K. Rappé, C. J. Casewit, K. S. Colwell, W. A. Goddard III, and W. M. Skiff, J. Am. Chem. Soc. 114, 10024 (1992).

http://dx.doi.org/10.1021/ja00051a040
http://dx.doi.org/10.1021/ja00051a041
http://dx.doi.org/10.1021/ja00051a042

It comes up with parameters based on the element, its hybridization and its
connectivity. It applies to the full periodic table!

How difficult would it be to implement this?   Given the current interest
in eg metals etc, it seems like a very valuable addition, and certainly extends
the Tripos field!
-- 

Henry Rzepa.
+44 (020) 7594 5774 (Voice); +44 (0870) 132 3747 (eFax); rzepahs at mac.com (iChat)
 http://www.ch.ic.ac.uk/rzepa/ Dept. Chemistry, Imperial College London, SW7  2AZ, UK.

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