I'm wondering what are those specifications that gaussview put right after my atoms coordinate in the input of the calculation? Is it redundant coordinates? It doesn't seem it is. You can see what I am talking about from my Notepad file.
Thank you.
Mathieu
Yep - Gaussview defaults to "geom=connectivity" and puts the atom connectivity (which atom is bonded to which others) in the input file - this is not required, and, if you don't like it (and your molecule is relatively small), just removed "geom=connectivity" from the # line and remove all of those extra lines of connectivity information, and Gaussian will run with cartesian coordinates and derivatives and be just fine -
Removing of connectivity from input has no influence on default algorithm of optimisation over internal coordinates. Optimisation with internal/redundant coordinates was shown to be computationally more efficient than optimisation in cartesian coordinates or Z-matrix (thats actually why it is default). However in some cases bad automatic adjustment of redundants turns in significant optimisation problems. In this case AddRedundant and similar options has to be used or optimisation in cartesians.
Connectivity in input is pure waste for all methods that do not have "bonds" - so for semiempirics, HF, DFT and all post-HF methods, so almost all functionality of Gaussian.
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