From 7f83a351a8f26321f7b4176e56ddf2bc595f4064 Mon Sep 17 00:00:00 2001 From: Mohamed Belkacem Date: Mon, 23 Apr 2018 15:10:05 +0200 Subject: [PATCH] Updates to publications and links --- .DS_Store | Bin 8196 -> 8196 bytes analysis/detail1.html | 15 +- analysis/detail2.html | 2 +- publications.html | 1264 ++++++-------------------------------- publications.html.bak | 176 ++++++ publications_old.html | 1088 ++++++++++++++++++++++++++++++++ pubs.html.bak | 10 + research.html | 2 +- tddft-md/detailQMMM.html | 4 +- tddft-md/formal.html | 16 +- tddft-md/formal.html.bak | 477 +------------- 11 files changed, 1477 insertions(+), 1577 deletions(-) create mode 100644 publications.html.bak create mode 100644 publications_old.html create mode 100644 pubs.html.bak diff --git a/.DS_Store b/.DS_Store index 343f28565b8564f7f5495a9048e747f90d4085ba..14f4de988cb145d8498cf33c9fca38d9c7800b3f 100644 GIT binary patch delta 107 zcmZp1XmQwZLSV9hpy=ki0_rS^q6`HLr3^_7ISiQ$$qb1MB|ti#A&;S$As$HQFr-XA VC@itrRP+?nW_F3c#H&Bf1OWLd8^-_u delta 99 zcmZp1XmQwZLV%HRvY?>I=DPywERuo@1q`JONenp*nGDGci3}w`I-enrp?LB^VTsMQ SqNkW97I184m-tJZQdR&dG8&fv diff --git a/analysis/detail1.html b/analysis/detail1.html index 08cb086..0127d8e 100644 --- a/analysis/detail1.html +++ b/analysis/detail1.html @@ -56,12 +56,11 @@ absorption spectrum which has a pronounced collection of strength in the region of the Mie plasmon. TDLDA driven with small amplitude excitations allows to explore the optical - response [9]. The + response [Cal97]. The figure beneath shows results for Na8+ as - example (taken from [???]) + example (taken from [Leg06]) in comparison to experiment (upper panel) and CI calculations - (???)(second from above). The + (second from above). The overall position of the peak strength is nicely reproduced by all methods, even by the semiclassical approach. CI produces the most detailed spectrum. The green bars show the discrete @@ -86,10 +85,10 @@ Laser induced direct photo-emission of electrons allows to conclude on the clusters single-electron states by measuring the photo-electron spectra (PES). TDLDA with appropriate - self-interaction correction (SIC) [277] - allows to simulate that process in detail [251] + self-interaction correction (SIC) [Leg02] + allows to simulate that process in detail [Poh00] . The figure to the left shows two examples for two clusters - which are nearly spherical (taken from [304]). + which are nearly spherical (taken from [Poh03]). The arrows indicate the level classification according to principal quantum number and angular momentum. The PES depend, of course, on the direction of emission (checked here are the @@ -112,7 +111,7 @@ allows an enormous manifold of P&P scenarios. The figure to the right sketches a simple and robust scenario for a nearly spherical cluster, actually Na41+ - [290]. The idea is to + [And02]. The idea is to map the radius vibrations of the cluster by an off-resonant laser pulse. The pump pulse ionizes the Na41+ within 50 fs by three more charge units, see second panel from diff --git a/analysis/detail2.html b/analysis/detail2.html index d8997a5..c18c708 100644 --- a/analysis/detail2.html +++ b/analysis/detail2.html @@ -60,7 +60,7 @@ The figure to the right shows the result of a molecular dynamics simulation of electronic and ionic dynamics of Na41+ - under the influence of strong laser fields [332]. + under the influence of strong laser fields [Bel06]. Ionization is drawn as function of laser intensity. One sees a sharp kink at a critical intensity of I = 1016 W/cm2. diff --git a/publications.html b/publications.html index 3f5300f..e628b35 100644 --- a/publications.html +++ b/publications.html @@ -1,1088 +1,176 @@ - - - - -Theory of Cluster Dynamics - - - - -
- - - + Theory of Cluster Dynamics
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+ + + diff --git a/pubs.html.bak b/pubs.html.bak new file mode 100644 index 0000000..9c10a7a --- /dev/null +++ b/pubs.html.bak @@ -0,0 +1,10 @@ + Theory of Cluster Dynamics
\ No newline at end of file diff --git a/research.html b/research.html index bf218a2..6e9666b 100644 --- a/research.html +++ b/research.html @@ -1 +1 @@ - Theory of Cluster Dynamics

Our Research Activities

A scientific guide

The core of our activities concerns the theoretical analysis of the dynamics of molecules and clusters. The method of choice for most of our studies is time-dependent density functional theory. One can sort our activities along three major directions of research: intrinsic dynamical system properties investigated with moderate external excitations (perturbative regime), response to strong external fields analyzed with a bunch of different observables taking care particularly of information from electron emission, and development of the necessary numerical as well as theoretical tools. The majority of applications deals with free molecules and clusters. One branch of studies deals also with clusters in contact with polarizable media (raregas matrices, insulating surfaces).

Theoretical developments

Understanding of cluster dynamics requires elaborate theoretical tools. Time-Dependent Density Functional Theory (TDDFT) represents here a robust starting point which allows to address a great variety of situations. We use TDDFT at various levels of sophistication. Basis is the most efficient, Time-Dependent Local-Density Approximation (TDLDA). It is augmented by a Self-Interaction Correction (SIC) for a proper description of electron emission and associated observables. Ionic motion is propagated simultaneously by classical Molecular Dynamics (MD) amounting together to TDLDA-MD. Very energetic processes allow semi-classical approximations for which we use mostly the Vlasov-LDA approximation. The latter allows a relatively simple extension by dynamical correlations with a collision term which accounts properly for the Pauli principle leading to the Vlasov-Uehling-Uhlenbeck (VUU) equation.
Recent developments focus on the implementation of such dynamical correlations in the fully quantum mechanical framework of TDLDA. A robust, phenomenological route is followed with the Relaxation-Time Approximation (RTA) known from bulk matter and implemented now for finite Fermion systems. An exact evaluation of the quantum-mechanical collision is prohibitively expensive. With Stochastic TDLDA (STDLDA), we render the case manageable by a stochastic evaluation of the collisions. Full STDLDA can cope even with large fluctuations of the mean field as they are typical for violent dynamical processes. Further savings are possible in the regime of small statistical fluctuations which allows to use one average mean field delivering Average STDLDA (ASTDLDA). In any case, the dynamical correlations thus implemented allow a pertinent description of dissipation in electron dynamics which becomes an important ingredient at longer times (in metal clusters typically > 50 fs).
Numerically, we solve TDLDA and related approaches in coordinate-space grid representations, fully three-dimensional if necessary and in the much faster cylindrically symmetric 2D grid if the case allows. All grids are surrounded bands generating absorbing boundary conditions to allow a correct description and analysis of electron emission.

Intrinsic dynamical properties of molecules and clusters

At moderate perturbations, the system response dominantly reflects its own (structure and dynamical) properties. The most prominent feature is the optical response which characterizes the coupling of photons to the electrons of the system. We obtain it from TDLDA driven in the regime of weak perturbations [--> link to AnnPhys Calvayrac 1997]. As optical response is the doorway to almost all further dynamical processes, it is regularly scanned before starting with more involved scenarios (see below).
The ionic dynamics of molecules and clusters is explored by pump and probe scenarios, again driven in the regime of moderate excitations to explore the system as such without too much perturbation.

Free clusters in strong external fields

When applying stronger external fields, a world of dynamical scenarios is opened as, e.g., multi-photon ionization, higher harmonic generation, multi-fragmentation, or Coulomb explosion [--> link to RevModPhys Fennel 2010].
A large part of our activities is concerned with dynamical information which can be obtained from electron emission. The simplest and most widely used observable is the net ionization, often in connection with time resolved measurements. The trends of ionization with systematically varied laser parameters (frequency, intensity, pulse length, delay times) contain already a lot of valuable information. More can be obtained by looking at the emitted electrons in detail collecting the distributions of kinetic energies, called Photo-Electron Spectra (PES), or angular directions, in the ideal case even both together as Angular Resolved PES (ARPES). Our numerical tools (coordinate-space representation with absorbing boundary conditions) to solve TDLDA allow a rather convenient computation of all these detailed distributions, if needed even in time resolved manner. We apply them to simulate measurements in raregas atom, metal clusters, and C60 [--> link to PhysRep Wopperer 2015].
The detailed distributions ARPES indicate indicate limitations of a mere mean-field description as in TDLDA. They overestimate, e.g., the forward/backward emission along the laser polarization axis. This calls for dissipation in electron dynamics as it is given by dynamical correlations. This is the main line of present development and applications.

Molecules and clusters in contact with a polarizable environment

Clusters can be more easily handled experimentally when they are produced in contact with an environment (deposited on a surface or embedded in a matrix). Thus a large amount experimental data was produced under these conditions. We have thus developed a simplified description of the environment in terms of classical Molecular Mechanics (MM) taking care to include a proper modeling of its dynamical polarizability. This is coupled to the standard Quantum-Mechanical (QM) handling of the electron cloud in the active molecule or cluster, yielding together QM/MM method. This hierarchical approach allows us to explore various dynamical scenarios, as optical response of deposited clusters, deposition processes, irradiation of embedded clusters by an intense laser field, etc with sufficiently large samples for the environment [--> link to PhysRep Dinh 2009].

\ No newline at end of file + Theory of Cluster Dynamics

Our Research Activities

A scientific guide

The core of our activities concerns the theoretical analysis of the dynamics of molecules and clusters. The method of choice for most of our studies is time-dependent density functional theory. One can sort our activities along three major directions of research: intrinsic dynamical system properties investigated with moderate external excitations (perturbative regime), response to strong external fields analyzed with a bunch of different observables taking care particularly of information from electron emission, and development of the necessary numerical as well as theoretical tools. The majority of applications deals with free molecules and clusters. One branch of studies deals also with clusters in contact with polarizable media (raregas matrices, insulating surfaces).

Theoretical developments

Understanding of cluster dynamics requires elaborate theoretical tools. Time-Dependent Density Functional Theory (TDDFT) represents here a robust starting point which allows to address a great variety of situations. We use TDDFT at various levels of sophistication. Basis is the most efficient, Time-Dependent Local-Density Approximation (TDLDA). It is augmented by a Self-Interaction Correction (SIC) for a proper description of electron emission and associated observables. Ionic motion is propagated simultaneously by classical Molecular Dynamics (MD) amounting together to TDLDA-MD. Very energetic processes allow semi-classical approximations for which we use mostly the Vlasov-LDA approximation. The latter allows a relatively simple extension by dynamical correlations with a collision term which accounts properly for the Pauli principle leading to the Vlasov-Uehling-Uhlenbeck (VUU) equation.
Recent developments focus on the implementation of such dynamical correlations in the fully quantum mechanical framework of TDLDA. A robust, phenomenological route is followed with the Relaxation-Time Approximation (RTA) known from bulk matter and implemented now for finite Fermion systems. An exact evaluation of the quantum-mechanical collision is prohibitively expensive. With Stochastic TDLDA (STDLDA), we render the case manageable by a stochastic evaluation of the collisions. Full STDLDA can cope even with large fluctuations of the mean field as they are typical for violent dynamical processes. Further savings are possible in the regime of small statistical fluctuations which allows to use one average mean field delivering Average STDLDA (ASTDLDA). In any case, the dynamical correlations thus implemented allow a pertinent description of dissipation in electron dynamics which becomes an important ingredient at longer times (in metal clusters typically > 50 fs).
Numerically, we solve TDLDA and related approaches in coordinate-space grid representations, fully three-dimensional if necessary and in the much faster cylindrically symmetric 2D grid if the case allows. All grids are surrounded bands generating absorbing boundary conditions to allow a correct description and analysis of electron emission.

Intrinsic dynamical properties of molecules and clusters

At moderate perturbations, the system response dominantly reflects its own (structure and dynamical) properties. The most prominent feature is the optical response which characterizes the coupling of photons to the electrons of the system. We obtain it from TDLDA driven in the regime of weak perturbations [Cal97]. As optical response is the doorway to almost all further dynamical processes, it is regularly scanned before starting with more involved scenarios (see below).
The ionic dynamics of molecules and clusters is explored by pump and probe scenarios, again driven in the regime of moderate excitations to explore the system as such without too much perturbation.

Free clusters in strong external fields

When applying stronger external fields, a world of dynamical scenarios is opened as, e.g., multi-photon ionization, higher harmonic generation, multi-fragmentation, or Coulomb explosion [Fen10].
A large part of our activities is concerned with dynamical information which can be obtained from electron emission. The simplest and most widely used observable is the net ionization, often in connection with time resolved measurements. The trends of ionization with systematically varied laser parameters (frequency, intensity, pulse length, delay times) contain already a lot of valuable information. More can be obtained by looking at the emitted electrons in detail collecting the distributions of kinetic energies, called Photo-Electron Spectra (PES), or angular directions, in the ideal case even both together as Angular Resolved PES (ARPES). Our numerical tools (coordinate-space representation with absorbing boundary conditions) to solve TDLDA allow a rather convenient computation of all these detailed distributions, if needed even in time resolved manner. We apply them to simulate measurements in raregas atom, metal clusters, and C60 [Wop15].
The detailed distributions ARPES indicate indicate limitations of a mere mean-field description as in TDLDA. They overestimate, e.g., the forward/backward emission along the laser polarization axis. This calls for dissipation in electron dynamics as it is given by dynamical correlations. This is the main line of present development and applications.

Molecules and clusters in contact with a polarizable environment

Clusters can be more easily handled experimentally when they are produced in contact with an environment (deposited on a surface or embedded in a matrix). Thus a large amount experimental data was produced under these conditions. We have thus developed a simplified description of the environment in terms of classical Molecular Mechanics (MM) taking care to include a proper modeling of its dynamical polarizability. This is coupled to the standard Quantum-Mechanical (QM) handling of the electron cloud in the active molecule or cluster, yielding together QM/MM method. This hierarchical approach allows us to explore various dynamical scenarios, as optical response of deposited clusters, deposition processes, irradiation of embedded clusters by an intense laser field, etc with sufficiently large samples for the environment [Din09].

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- - - + Theory of Cluster Dynamics
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