Re: [cclib-devel] normal modes and vibdisps

[Noel O'B. <bao...@gm...>]

2008/7/22 Adam Tenderholt <a-t...@st...>:
> What are the differences between normal modes and cartesian
> displacement vectors? I think Gaussian uses the latter, while ADF and
> ORCA use the former.

Isn't it just that the normal mode is the actual thing which is being
represented by a cartesian displacement vector? Perhaps if you look at
the normal modes of water for Gaussian, ADF and ORCA, it will make
things clearer?

> ADF doesn't use mass-weighted normal modes while
> ORCA does use mass-weighted NMs. Do we need to change the way our
> parsers are thinking about vibdisps?

I've been looking back at an earlier conversation with Mehdi who was
interested in the hessian. He said that mass-unweighted is preferred
as then you can use it to calculate the normal modes for different
isotopes and so on. I have a feeling that it's not possible to change
MW NM to UMW NM. If so, this may mean that we should have two
attributes instead of just one vibdisps.

> Adam
>
>
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