Re: [cclib-devel] etsecs conversions

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

On 27/03/07, Karol Langner <kar...@kn...> wrote:
> On Tuesday 27 of March 2007 14:21, Noel O'Boyle wrote:
> > This code may be old and creaky, but the general idea was as follows:
> >
> > (1) You multiply by two because for an excitation from a
> > doubly-occupied orbital there are two excitations in fact...one
> > involving the alpha electron and one involving the beta electron. For
> > an unrestricted calculation, you shouldnt multiple by two.
>
> GAMESS, for example, prints the excitations of both alpha nad beta electrons,
> even for restricted calculations (see test file "water_cis.out"). The
> coefficients alpha and beta electrons are always the same.
>
> > (2) You square because that is the definition of etsecs. It is a
> > somewhat arbitary definition so I am happy to change it. The idea is
> > that these sqr values somehow represent the fractional contribution of
> > a particular SEC to the whole transition. Unfortunately, at least in
> > TD-DFT, this is almost but not exactly true (i.e. these fractional
> > contributions dont add to 1). In fact, this is probably a good unit
> > test to have to make sure that all parsers are doing the same thing.
>
> So we can't really test if they sum up to 1, since they don't :)

Sorry - I should have been more clear. They almost sum to 1, and so an
assertInside would still be a useful test since if the values sum to
something quite different than 1, there is some problem. However, may
I suggest redefining etsecs to use the original positive or negative
coefficients. The test should use the squared values though. I know we
shouldn't redefine the API in a point release, but I feel no
responsibility towards API attributes that we didn't test rigourously.

> Another point: as far as I can see, there's no way to force Jaguar to print
> out triplet excited states.
You're saying that it is possible to do the calculation, but just not
print out the results?

> Karol
>
> --
> written by Karol Langner
> Tue Mar 27 15:25:35 CEST 2007
>