Hierarchical method for the dynamics of clusters and molecules in contact with an environment

Hierarchical method for the dynamics of clusters and

molecules in contact with an environment

Molecules/clusters + environment

(embedded/deposited)

Fundamental studies on mechanisms

(Nano)Technological applications (size controlled

deposition…)

M. Baer, P. G. Reinhard (Erlangen), M. Dinh, ES (Toulouse)

Contacts with insulators (ionic crystals, rare gases…) Structure and low energy dynamicsIrradiation dynamics

Density Functional Theory (DFT)

Ensemble of orbitals (1 electron) / no correlation

One body density

Effective mean field theory (Kohn-Sham)

Model for free clusters

Explicit ions via pseudo potentials

Detail of structure + ionic Molecular Dynamics (MD)

Ions

Electrons

Kohn-Sham potential Ions + ext.

Local Density Approximation (LDA)

Exch. + Corr. Hartree

Self Interaction Correction (SIC)

Time Dependent (TD)LDA TDSIC !?

Metal cluster in an environment

Hierarchical approach:Model for free clusters +Polarizable matrix+ Couplings

Atoms Ar, Ne, Kr, MgO…

RI

Ions Na, K (Cs, Ag…)

Equations of motion by variationof total energyTDLDA for electrons

MD for ions

MD for atoms (positions AND dipoles)

Electrons i

Dipoles

Positions

@MgONa6

freeOptical response

Delicate balanceShort range compression (blue)Long range polarization (red)

Exp: Rostock

Optical response (cont’d)C

om

pre

ssio

n

Polarization Caution: « Helium blue shift »

More detailed investigations …

Na – Na ~ 800 meVAr – Ar ~ 50 meVNa -Ar ~ 5 meV

Response of environment Na6@Ar(100) Ekin = 800 meV

Charge

Distribution of dipole energy at time of impact

x [a0]

Key role of environment’s degrees of freedomSubtle energy exchanges

▶ Some open questions

Towards irradiation dynamics Clusters and « bio » molecules under irradiation (laser, ions…)

Formal difficulties SIC and beyond…, TDSIC…

Some conclusions and perspectives

▶ Low energy response of cluster’s in contact with an

environment

Hierarchical model

Microscopic electrons, classical polarization… (QM/MM)Delicate interplay of competing effects

Subtle energy balance

Key role of environment’s degrees of freedom