Psi-k - Ab initio (from electronic structure) calculation of complex processes in materials


Time-Dependent Density-Functional Theory: Prospects and Applications


CECAM/Ψk SCHOOL + WORKSHOP PROPOSAL

Time-Dependent Density-Functional Theory: Prospects and Applications

Organizers:

*) E. K. U. Gross
Institut fuer Theoretische Physik
Freie Universitaet Berlin
Arnimallee 14, D-14195 Berlin, Germany
Phone: +49-30-838-54784
Fax: +49-30-838-55258
Mail:
http://www.physik.fu-berlin.de/~ag-gross

*) Miguel A. L. Marques
Institut fuer Theoretische Physik
Freie Universitaet Berlin
Arnimallee 14, D-14195 Berlin, Germany
Phone: +49-30-838-53028
Fax: +49-30-838-55258
Mail:

*) Fernando Nogueira
Dep. de Física, Faculdade de Ciências e Tecnologia,
Universidade de Coimbra and
Centro de Física Computacional
Rua Larga, 3004-516 Coimbra, Portugal
Phone: +351-239410114
Fax: +351-239829158
Mail:
http://nautilus.fis.uc.pt/~fnog

*) Angel Rubio
Dpto. Fisica de Materiales, Facultad de Quimicas U. Pais Vasco,
Centro Mixto CSIC-UPV/EHU and
Donostia International Physics Center (DIPC)
Apdo. 1072, 20018 San Sebastian/Donostia, Spain
Phone: +34-943018292
Fax: +34-943015600
Mail:
http://dipc.ehu.es/arubio


Scientific content:

Time-dependent density-functional theory [1] (TDDFT) is an extension of density-functional theory [2] (DFT) to time-dependent problems, and can be viewed as an alternative formulation of time-dependent quantum mechanics. As in DFT, the the wave-function no longer has the leading role: the basic variable of TDDFT is the one-body electron density, n(r,t). The advantages are clear: a complex function in a 3N-dimensional space (where N is the number of electrons in the system) - the many-body wave-function - is replaced by a real function that depends solely on the 3-dimensional vector r - the density. Usually n(r,t) is obtained using an auxiliary system of non-interacting electrons that feel an effective time-dependent potential, the time-dependent Kohn-Sham potential. Its exact form is, however, unknown, and has to be approximated.

The Kohn-Sham scheme is perfectly general, and can be applied to essentially any time-dependent situation. However, if the time-dependent potential is weak, linear-response theory can be used to ease the calculations. In this way it is possible, e.g., to obtain optical absorption spectra that are in very good agreement with experimental results [3]. If the time-dependent potential is strong, a full solution of the Kohn-Sham equations is required. A canonical example of this regime are atoms or molecules in strong laser fields. In this case, TDDFT is able to describe non-linear phenomena like high-harmonic generation, or multi-photon ionization.

The use of TDDFT is increasing, and it is fast becoming one of the tools of choice to get accurate and reliable predictions for excited-state properties in solid state physics, chemistry and biophysics. However, in international meetings, schools and workshops, TDDFT has usually been just one of the topics covered. This means that scientists new to the field face difficulties in grasping its many aspects that could be alleviated if they could attend a school on TDDFT. We also believe that a school on TDDFT would be extremely helpful for young graduate students, post-docs and even older scientists that are envisaging a project for which TDDFT would be the tool of choice. For this reason we decided to organize a 10 day school on TDDFT, covering its theoretical, practical, and numerical aspects.

This school will be followed by an international workshop, where the new developments of TDDFT will be discussed. Students attending the Summer School will be encouraged to attend the workshop, so they can get in contact with state of the art research in the field of TDDFT. The purpose of the workshop is to bring together leading experts in the field of TDDFT with different backgrounds, like density functional, many-body, nuclear physics and quantum chemists. This will allow the exchange of ideas between the different fields and the creation of links between the traditionally separated communities. We believe that the intense and informal discussion which is possible in this kind of workshops can contribute to the formation of a strong community in the field of TDDFT. Some of the recent developments of TDDFT that will be covered during the workshop include TDDFT versus current-DFT [4,5], van der Waals interactions [6], applications to biological systems [7], new functionals [8,9], transport phenomena [10], optical spectra of solids [3], etc. It will assemble specialists in these and other areas and will consist of several presentations and round-tables.

References:
[1] E.K.U. Gross and W. Kohn, Adv. Quantum Chem. 21, 255 (1990).

[2] A Primer in Density Functional Theory, Vol. 620 of Lecture Notes in Physics, edited by C. Fiolhais, F. Nogueira, and M. A. L. Marques (Springer, Berlin, 2003).

[3] G. Onida, L. Reining and A. Rubio, Rev. Mod. Phys. 74, 601 (2002).

[4] G. Vignale and W. Kohn, Phys. Rev. Lett. 77, 2037 (1996); G. Vignale and M. Rasolt, Phys. Rev. Lett. 59, 2360 (1987)

[5] P.L. de Boeij, F. Kootstra, J.A. Berger, R. van Leeuwen, and J.G. Snijders, J. Chem. Phys. 115, 1995 (2001).

[6] M. Lein, J.F. Dobson, and E.K.U. Gross, J. Comput. Chem. 20, 12 (1999)

[7] M.A.L Marques, X. Lopez, D. Varsano, A. Castro, and A. Rubio, Phys. Rev. Lett. 90, 158101-1 (2003).

[8] L. Reining, V. Olevano, A. Rubio, and G. Onida, Phys. Rev. Lett. 88, 066404 (2002).

[9] Y.H. Kim and A. Goerling, Phys. Rev. Lett. 89, 096402 (2002); Phys. Rev. B 66, 035114 (2002).

[10] M. Di Ventra and N.D. Lang, Phys. Rev. B 65, 045402 (2001).


Tentative program for the school:

The school will be attended by a maximum of around 30 student, and will last 10 days, with theoretical sessions (mostly) in the mornings and practical (tutorial) sessions in the afternoons. The theoretical sessions will consist of two 1.5 hour lectures + 20 minutes for discussion. The practical sessions will last for 3 hours and a computer will be allocated for each two students. This will allow the students to have some time every day for studying and talking to the teachers. The program of the school starts with basic ground-state DFT, then continues with the theoretical and numerical aspects of TDDFT, and will end with an outline of some of its many applications.

The preliminary program is:

Day 1 m: Introduction to DFT (T)
a: A survey of xc functionals (T)

Day 2 m: Numerical methods: plane waves and real space methods (T)
a: Introduction to the codes + Ground-state DFT I (P)

Day 3 m: Pseudopotentials (1.5h, P); TDDFT I - Introduction (1.5h, T)
a: Ground-state DFT II (P)

Day 4 m: TDDFT II - Linear Response Theory (T)
a: Linear response theory for finite systems I - atoms (P)

Day 5 m: Propagation schemes (T)
a: Linear response theory for finite systems II - molecules (P)

Day 6 : Free day

Day 7 m: TDDFT III - Advanced topics (T)
a: Linear response for infinite systems I (P)

Day 8 m: Applications of TDDFT (T)
a: Linear response for infinite systems II (P)

Day 9 m: Toward biological systems (QM/MM techniques, bio-receptors) (T)
a: Numerical tests of propagation methods (P)

Day 10 m: TDDFT versus other approaches like BSE, current-DFT and Quantum
Chemistry methods (T)
a: Free afternoon

Tentative list of teachers:

During the school we will incentive a close and informal contact between the students and the teachers. Furthermore, the students will be stimulated to talk about their current research activities and future interests. We feel that this is an important point, since young scientists should be involved in the building up of a strong community.


The preliminary program of the workshop is:

The 4 day workshop will take place between the 8-12 September 2004. It will include both invited talks on key aspects of TDDFT (45m each), contributed talks (30m) and a poster session. The tentative list of invited speakers is

Format of the workshop:

We plan an informal workshop with sufficient time for discussions. The informal character of the talks will be encouraged and presentations which are partly tutorial, given the mixed character of the audience, are most welcome. The time for each talk will be divided into 75% for the presentation plus 25% discussion of discussion. Speakers will be encouraged to divide their available time into two separate parts if their topic falls under more than one heading.

We will select some posters from the young researchers participating in the workshop to be presented as oral communications.


Financial information and Co-sponsorship:

We estimate the conference cost to be about 40000 euro. That includes all the expenses of invited speakers, scholarships for selected young scientists, and additional costs like stationery, publicity, or abstract books. The Benasque Center for Science (http://benasque.ecm.ub.es/) will provide the local infrastructure (computers, meeting rooms, secretarial support, transportation, outdoor activities). We expect this event to be jointly funded by Ψk and CECAM, as well as by spanish institutions.

All the funding from the ESF Ψk Program will be used to provide financial support for graduate students and postdocs and thus encourage their active participation. Only young researchers participating in both school and workshop will be eligible for this financial support. We hope to offer 18 scholarships of 600 euro (350 for living allowance plus 250 for travel expenses). Therefore we apply for a total amount of 10800 euro.

The rest of the estimated cost is expected to be financed by the following sources (in parenthesis is the amount asked to each institution): Spanish Ministry of Science and Technology (12000 Euros), CECAM (8000 Euros), the Benasque Center, Donostia International Physics Center, and European Networks active in this field.


Location/Timing

We plan to organize this event at the "Benasque Center for Science", Benasque, Spain, from August 29, 2004 to September 11, 2004. Benasque is a beautiful town in the heart of the Pirinees. The school will take place from August 29 to September 7, and the workshop will start September 8 and finish on Sep. 12.


Participants

The call for participation will be mainly directed to students and scientists specialized on computational physics, quantum chemistry and biophysics. We will limit the number of participants to 60, in order to ensure a maximum interaction between all the scientists participating. Attendance of graduate students and postdocs will be strongly encouraged through the inclusion of short contributed talks and a poster session. Furthermore, we will award to Ph.D. students who present an outstanding poster short oral presentations.