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["Nuno A. G. Bandeira" <nuno.bandeira@ist.utl.pt>]

Xiulin Ruan wrote:

> Thanks for your reply. Our specific problem is to calculate the energy 
> levels of transition metal doped solids, like Ti3+ doped Al2O3, which is 
> an important laser material. The free-standing Ti3+ ion has 5 degenerate 
> d orbitals. After we put the ion in the Al2O3 host, the crystal field 
> splits these d orbitals so that d-d transitions become possible. These 
> transitions are utilized to make Ti:Al2O3 an excellent laser material. 
> We have used TDDFT (with Gaussian and CPMD) to calculate the excited 
> states of a Ti3+ doped cluster, and the energy levels are very good. 
> However we couldn’t figure out a way to implement the periodic host with 
> these packages. If we wanna extend our calculations by replacing the 
> finite cluster with the more realistic periodic solids, could the TDDFT 
> capability of abinit help?

What you're asking is almost unfeasible. The only software I know that 
can perform TDDFT on solids is ADF-Band, but for your specific case you 
have to build a very large unit cell with a large number of atoms to 
reproduce the doping.

TDDFT is hard enough as it is but with such a unit cell it would be a 
monumental task!

Not wanting to discourage you but if your numbers are good for the 
finite cluster why not use them instead ? It seems that since only t2g-> 
eg transitions are of importance to you, the exact reproduction of the 
doped Al2O3 crystal should not be imperative. This would only be an 
issue I think if you were looking for transitions based on the Al-O bond.

But then if money or resources are no object you can purchase as many 
licenses of Band as you wish and install them on as many machines.

--
Nuno A. G. Bandeira, AMRSC
Graduate researcher and molecular sculptor
Inorganic and Theoretical Chemistry Group,
Faculty of Science
University of Lisbon - C8 building, Campo Grande,
1749-016 Lisbon,Portugal
http://cqb.fc.ul.pt/intheochem/nuno.html
Doctoral student @ IST,Lisbon
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