196 lines
6.1 KiB
HTML
196 lines
6.1 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<title>Theory of Cluster Dynamics</title>
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<li style="margin-top:1px;border-top:1px solid #B0C4DE; "><a href="../index.html">Home</a></li>
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<li><a href="../intro.html">Introductory Overview</a></li>
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<p><font color="white" size="6"><b>Theory of Cluster Dynamics</b></font><font size="5"><br>
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</font><font size="6">
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</font><font size="5">The Toulouse - Erlangen Collaboration</font></p>
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</div>
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<div id="content">
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<div style="margin:15px;width:770px;border:1px solid gray;float:left;font-size:10px;">
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<div style="width:220px;float:left;text-align:center;">
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<a href="../intro.html">1. What are clusters? </a>
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</div>
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<div style="width:220px;float:left;text-align:center;">
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<a href="../dynamics.html"> 2. Why study cluster dynamics?</a>
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</div>
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<div style="width:220px;float:left;text-align:center;font-weight:900;font-size:12px;">
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<a href="our_dynamics.html"> 3. How we deal with cluster dynamics </a>
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</div>
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</div>
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<div id="WideContent">
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<div id="contentBoxWide">
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<div id="contentBoxHeader">
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<p>Dynamics </p>
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<div id="contentBoxContent">
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<div style="text-align: center;">
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<div style="text-align: justify;">
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<h1>How we deal with cluster dynamics<br>
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</h1>
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The understanding of the complicated dynamical scenarios such as the
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ones described previously requires dedicated theoretical modelling.
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Cluster physics and even more so cluster dynamics lays at the interface
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of several fields of science, especially chemistry and physics. The
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theory of cluster dynamics has thus borrowed inspiration from these
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various domains to develop its own and original methods. <br><br>
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Not surprisingly, a direct transposition of methods well developed in a
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given field only provides guidelines and a starter for further
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developments. Still, it also allows to benchmark new developments on
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well established test cases. Cluster dynamics has thus benefited a lot
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from experience gained in chemistry, especially at the side of moderate
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excitation, and in physics for more violent scenarios, especially from
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solid state and nuclear physics. The description of cluster dynamics is
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made difficult by two basic problems: The fact that one would like to
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deal with large (although finite) systems and the fact that electrons
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and ions move at awfully different time scales (typically a factor
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100). This implies huge simulation times to be able to resolve
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simultaneously electronic and ionic dynamics. One thus needs both
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robust and simple approaches to overcome these two difficulties of time
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scales and system size.<br>
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<br>
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<table style="border: 0px; float: left;">
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<tr>
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<td>
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<a href="laser.html">
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<img alt="laser"
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src="laser_slide_small.jpg"
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style="border: 0px solid ; width: 527px; height: 275px; float: left;">
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</a>
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</td>
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<tr>
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<td align="center">
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<b>
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Fig.1:
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Irradiation of Na<sub>9</sub><sup>+</sup> by a laser pulse.
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</b>
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</td>
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</tr>
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</table>
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In the case of violent excitation, the most robust and simple approaches
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rely on Density Functional Theory, a theory developed since the mid
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60's for electronic systems and which has met impressive successes, in bulk materials
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as well as in finite molecules. <br><br>
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<font color="red"><b>???In density functional
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theory, the complicated many-body electronic problem is simplified as
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it can be shown that the one body electronic density constitutes a key
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ingredient, espcially for computing the energy of the system. The
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extension of this theory to truly time-dependent processes is more
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recent and still in development and cluster dynamics offers here a
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fascinating domain of applications and testing.???</b></font> <br><br>
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In order to illustrate
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the capabilities of such methods we present here two examples of
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cluster response to violent external excitation. Figure 1 shows the
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irradiation of Na<sub>9</sub><sup>+</sup> by a laser pulse, while Figure 2
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displays a collision of Na<sub>9</sub><sup>+</sup> with Ar<sup>8+</sup>
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considered as an energetic projectile. The actual dynamical scenarios can be
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visualized through the two movies below (click on the image to download
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the corresponding movie). Various characteristics of the dynamics,
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especially in
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terms of time scales, are presented in both figures. These cartoons
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demonstrate strong interactions between electrons and ions and a
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complex non-adiabatic dynamics.<br>
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<table>
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<tr>
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<td>
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<a href="projectile.html"><img alt="projectile"
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src="proj_slide_small.jpg"
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style="border: 0px solid ; width: 518px; height: 276px;">
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</a>
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</td>
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<td align="left">
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<b>
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Fig.2:
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Collision of Na<sub>9</sub><sup>+</sup> with Ar<sup>8+</sup>
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</b>
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</td>
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</tr>
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</table>
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<br>
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