CMSP Seminar Series @ICTP Stasi Rm Thursday 25 January 11am - Mauro STENER

[CM Section]

ICTP Seminar Series in Condensed Matter and Statistical Physics
----------------------------------------------------------------------------------------- 


Thursday 25 January at 11:00 a.m.

Luigi Stasi Seminar Room, first floor, ICTP Leonardo building
*********************************************************************

Speaker:
Mauro STENER
(Dipt. di Scienze Chimiche e Farmaceutiche, Univ. di Trieste)

Title:
A New Efficient Time Dependent Density Functional Algorithm for
Large Systems:Theory, Implementation and Plasmonics Applications

Abstract:
A new algorithm to solve the TDDFT equations in the space of the density
fitting auxiliary basis set has been developed and implemented in ADF.^1
The TDDFT equations are recast to a non-homogeneous linear system,
whose size is much smaller than in Casida formulation, allowing to
calculate a wide portion of the absorption spectrum for large systems. The
method extracts the spectrum from the imaginary part of the 
polarizability at
any given photon energy, avoiding the bottleneck of Davidson 
diagonalization.
The original idea which made the present scheme very efficient consists in
the simplification of the double sum over occupied-virtual pairs in the 
definition
 of the dielectric susceptibility, which allows an easy calculation of 
such matrix
as a linear combination of constant matrices with photon energy dependent
coefficients. The method has been applied to very different systems in 
nature
and size (from H_2 to [Au_309 ]^- )^2,3 . In all cases, the maximum 
deviations found f
or the excitation energies with respect to Casida approach are below 0.2 
eV.
The new algorithm has the merit to calculate the spectrum at whichever 
photon
energy but also to allow a deep analysis of the results, in terms of 
Transition
Contribution Maps,^4 plasmon scaling factor analysis^5 , induced density 
analysis,
and with a fragment projection analysis^6 . Circular Dichroism of large 
systems
becomes also affordable.^7

*References***

1.O. Baseggio, G. Fronzoni and M. Stener, /J. Chem. //Phys/., *2015*, 
/143/, 024106.
2.O. Baseggio, M. De Vetta, G. Fronzoni, M. Â Stener, L. Sementa, A. 
Fortunelli and
A. Calzolari, /J. Phys. //Chem. C/, *2016*, /120/, 12773.
3. A. Fortunelli, L. Sementa, V. Thanthirige, T. Jones, M. Stener, K. 
Gagnon, A. Dass,
G. Ramakrishna, /J. Phys. Chem. Lett/, *2017*, /8/, 457.
4.  S. Malola, L. Lehtovaara, J. Enkovaara and H. Häkkinen, /ACS Nano/ 
*2013, */7,/ 10263.
5.  S. Bernadotte, F. Evers, C. R. Jacob, /J. Phys. //Chem. C/*2013, 
*/117/, 1863.
6. L. Sementa, G. Barcaro, O. Baseggio, M. De Vetta, A. Dass, E. Aprà , 
M. Stener,
A. Fortunelli, /J. Phys. Chem. C/ submitted.
7. O. Baseggio, D. Toffoli, G. Fronzoni, M. Stener, L. Sementa, A. 
Fortunelli /J. Phys.
Chem. C/, *2016*, /120/, 24335.