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Theoretical and Computational Materials Science. TETY. Photonic, Phononic and Meta- Materials. Materials Theory. C. Soukoulis. I. Remediakis. M. Kafesaki (to be appointed). G. Kopidakis. Materials Theory Group (est. 2007).

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Theoretical and Computational Materials Science


Photonic, Phononic and Meta- Materials

Materials Theory

C. Soukoulis

I. Remediakis

M. Kafesaki (to be appointed)

G. Kopidakis

materials theory group est 2007
Materials Theory Group (est. 2007)

C. Motsanos, N. Galanis, C. Mathioudakis, G. Kopidakis, I.Remediakis, E. Tylianakis, G. Barmparis, S. Stamatiadis (not shown: G. Kwtsopoulou, A. Maniadaki, G. Vantarakis, E. Pantoulas (graduated), K. Moratis (graduated))

Members: two faculty (I.R, G.K), one adjunct (C.M), five students (four PhD, one undergraduate), one staff.


Core courses (programming, solid-state physics, quantum mechanics).

Advanced courses (group theory, electronic structure).

~ 1 diploma thesis/year.

4 PhD students, 1 graduated.

2 ‘Manasaki’ best graduate student awards.

from atomistic simulations electronic structure theory
From atomistic Simulations - Electronic Structure Theory...

Empirical Force Fields plus Classical Monte-Carlo and Molecular Dynamics Simulations.

Quantum mechanical simulations (Tight-binding / LCAO).

Ab initio simulations (Density-functional Theory - DFT).

Variety of home-made, commercial and open-source codes running on a Beowulf cluster of ~60 nodes.

to computer aided design of new materials
… to computer-aided Design of new Materials

Surface chemistry and catalysis.

Carbon-based materials and other superhard ceramics.

Quantum dots, nanocrystals, nanowires.

Non-linear dynamics, energy localization and transfer.

All-optical signal processing and firewalls.

Hydrogen storage.


Nano is different

Gold is noble

...but nano-gold is a superb catalyst.

Left: Jewel from Malia, Crete, Greece (ca. 1800 BC);

Right: CO oxidation on Au nanoparticle

(Remediakis, Lopez, Nørskov, Angew. Chem. (2005)).

See also: “Making Gold Less Noble”, Mavrikakis et al., Catal. Lett. (2000).


Virtual catalyst for NH3 synthesis

Operation of this catalyst is a pure nano-effect.

K. Honkala, A. Hellman, I. N. Remediakis, A. Logadottir,

A. Carlsson, S. Dahl, C.H. Christensen and J. K. Nørskov,

Science, 307 558 (2005);

Surf. Sci., 600, 4264 (2006); Surf. Sci., 603, 1731 (2009).

si quantum dots in a sio 2








Si quantum dots in a-SiO2

Red : {100} Blue : {110}

Green : {121}

G. Hadjisavvas, I. N. Remediakis, P. C. Kelires, Phys. Rev. B 74, 165419 (2006);

On-going collaboration with R. Kalia and P. Vashishta, USC.


Shape of diamond nanocrystals in

amorphous Carbon

G. Kopidakis, I. N. Remediakis, M. G.

Fyta and P. C. Kelires, Diam. Rel.



, 1875 (2007).

au nanoparticles in co gas
Au nanoparticles in CO gas

G. D. Barmparis & I. N. Remediakis, in preparation.


Theoretical and Computational Materials Science


theory and modeling in materials physics
Theory and modeling in materials physics
  • Understand and control properties of materials with fundamental and practical interest from the bottom up by developing and using atomic-scale computational and theoretical tools
  • Simple models for fundamental understanding
    • General physical phenomena of wide applicability
    • Novel concepts of general validity
    • Qualitative results
  • Realistic models for accurate predictions
    • Atomistic computer simulations well suited for applications at nanoscale
    • Direct comparison with experiments
  • Current activities
    • Nonlinear wave localization and propagation
    • Structural, mechanical, electronic, optical properties of amorphous and nanostructured materials
    • Practical applications in ICT, “green” technologies
localization in nonlinear disordered systems
Localization in nonlinear disordered systems
  • Widely used toy models in condensed matter (polarons, excitons) nonlinear optics, photonics, BECs

Results often confirmed by realistic calculations

  • Discrete linear models
    • Periodic (homogeneous lattices)


    • Disordered (inhomogeneous)

Anderson localization

  • Discrete nonlinear models
    • Periodic, localization without disorder
    • Disordered ? GK, Aubry PRL 2000
  • Interplay of disorder and nonlinearity
    • Mathematical and numerical results
    • Experimental confirmation

Lahini et al PRL 2008

localization in isolated nonlinear disordered systems
Localization in isolated nonlinear disordered systems
  • Anderson localization not destroyed by nonlinearity

GK, Komineas, Flach, Aubry PRL 2008, Johansson, GK, Aubry EPL 2010

Propagation in driven nonlinear disordered systems

Johansson, GK, Lepri, Aubry EPL 2009

Transmission thresholds for amplitude of driving field

Self-induced transparency

targeted transfer of nonlinear excitations
Targeted transfer of nonlinear excitations
  • Understand and control propagation phenomena in complex systems
  • Ultrafast electron transfer in photosynthetic reaction centers

not thermally activated, nonlinear dynamical theory


Aubry, GK JBP 2005

amorphous and nanostructured carbon
Amorphous and nanostructured carbon
  • Relate macroscopic properties and experiment to atomic bonding through simulation
  • Tight-binding molecular dynamics

More efficient than first principles, more accurate than empirical potential


  • Atomic structure, mechanical, electronic, optical properties

Mathioudakis, GK, Kelires, Wang, Ho

PRB 2004

amorphous and nanostructured carbon1
Amorphous and nanostructured carbon

Accurate calculation of imaginary part

of dielectric function

Mathioudakis, GK, Patsalas, Kelires DRM 2007

nanodiamond in a c
Nanodiamond in a-C
  • link atomic level structure with optoelectronic response

Vantarakis, Mathioudakis, GK, Wang, Ho, Kelires PRB 2009

Diamond, a-D

Density sp3 fraction

3.24 g/cm3 88%

2.91 g/cm3 71%

2.58 g/cm3 51%

mechanical properties of nanocrystalline materials
Mechanical properties of nanocrystalline materials
  • Hall-Petch effect for metals

Hardness and yield strength increase with decreasing grain size

  • ‘Reverse’ Hall-Petch

Softening when grain size is in nanometer range

  • Optimum grain size for strongest material

Crossover from dislocation-dominated plasticity

to grain-boundary sliding

  • dependence of elastic properties

on grain size?

Softening not limited to plastic


  • What about non-metals?

Softening for non-metals,

such as diamond.


mechanical properties of nanocrystalline materials1
Mechanical properties of nanocrystalline materials
  • Universal laws for softening of nanocrystalline materials
    • Emerge from our studies of elastic response of very different

materials, such as copper and diamond.

    • Appear to be general, independent of chemical composition of


    • Derived from general considerations of

increasing fraction of grain boundary atoms.

Galanis, Remediakis, GK

PSS 2010

mechanical properties of nanocrystalline materials2
Mechanical properties of nanocrystalline materials
  • Similar softening for ultra-nanocrystalline diamond

Remediakis, GK, Kelires AM 2008

all optical processing
All-optical processing

Optical transmission rates at hundreds Gb/s

Electronic processors at a few Gb/s

Bridge the gap by

successfully implementing network security

operations ‘on the fly’

No optical to electronic

(and back) conversion

R. Webb et al IEEE JSTQE 2011

external collaborators
External Collaborators

S. Aubry Saclay, France

M. Johansson Linkoping, Sweden

K-M. Ho Ames, USA

C-Z. Wang

P. Kelires Lemessos, Cyprus

J.K. Norskov Stanford, USA

H. Hakkinen Jyvaskyla, Finland

K. Honkala


Theoretical and Computational Materials Science