The ABINIT Users Mailing List ( CLOSED )

["Xiulin Ruan" <ruan@purdue.edu>]

Dear Xavier,

 

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?

 

Thanks,

 

Xiulin  

 

---

From: Xavier Gonze [mailto:gonze@pcpm.ucl.ac.be]
Sent: Wednesday, June 20, 2007 1:38 PM
To: forum@abinit.org
Cc: myrta gruening
Subject: Re: [abinit-forum] TDDFT for periodic system

 

Dear Hua,

 

On 20 Jun 2007, at 04:33, hbao@purdue.edu wrote:

Dear all,

 

I am interested in calculating the energy level using TDDFT. I know that abinit is able to do TDDFT at calculate gamma point. How about periodic systems? Is TDDFT implement for k-points in abinit?

 

TDDFT with LDA and RPA kernels does not change the band edges of the periodic solids.

It is a fundamental problem with this approach when it comes to applications to solids.

 

In ABINIT, the Casida framework is implemented, and in

this framework, TDDFT for periodic solid is useless, giving the same results as straight DFT,

so we did not care about the non-Gamma case.

Myrta Gruening worked recently on this topics with me, and she will send you a preprint of ours

when ready.

 

TDDFT might be useful for solids in other contexts, though. See :

Onida G, Reining L, Rubio A

Electronic excitations: density-functional versus many-body Green's-function approaches

REVIEWS OF MODERN PHYSICS 74 (2): 601-659 APR 2002

and/or

Botti S, Schindlmayr A, Del Sole R, et al.

Time-dependent density-functional theory for extended systems

REPORTS ON PROGRESS IN PHYSICS 70 (3): 357-407 MAR 2007

 

Xavier