[molpro-user] How to do the double d-shell casscf calculation ??

[Wanyi Jiang]

Xiaobin,

Like you said, a double d-shell description is required in the active
space for late 3d transition metals.  Late 3d transition metals do not
have a sufficient number of anti-bonding orbitals for a well balanced
active space if only 3d orbitals are included. Diffuse functions are
an additional set of basis set functions used to improve the
description of the tails of orbitals far away from nuclei.  The
insufficiency of active space is not necessarily ameliorated by adding
diffuse basis set functions.

Your example clearly states the way to include 4d orbitals in the
active space. You may refer to the Molpro manual for technical
details.

Wanyi

On Sun, Dec 9, 2012 at 7:29 PM, 章晓斌 <n100420094 at fzu.edu.cn> wrote:
>
> Dear Molpor Users,
>
> I want to do some casscf calculations for nickel oxides.I know that
> transition metal chemistry (1st row) sometimes requires a double d-
> shell descriptionin the active space.
>
> The question is that：
> Should I include the 4d orbital or just use more diffuse basis set?
>
> For example, in article the author says that：
>
> "To model correlation in the d shell and to include the double-shell
> effect, all occupied Fe 3d orbitals (72a, 73a and 45b) were correlated
> by 4d orbitals (76a, 77a and 46b)and the bonding orbitals were descr-
> ibed with antibonding correlating orbitals."
>
> And how to add the 4d orbital?
>
> Best regards,
> Xiaobin Zhang
>
>
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