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Exploring the importance of quantum effects in nucleation: The archetypical Ne n case
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10.1063/1.4730033
/content/aip/journal/jcp/137/1/10.1063/1.4730033
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/1/10.1063/1.4730033

Figures

Image of FIG. 1.
FIG. 1.

Definition of various energetic quantities used in the main text. The energy zero is taken as the situation of infinite separation and complete rest for all the Ne atoms. X stands for classical, ZPAD, or G-TDH simulation method. V min (n) is the minimum of the Ne n potential energy, and is the energy of the Ne n ground state level for method X. Note that . is defined as the binding energy of the nth Ne atom for method X, i.e., . E is the total energy of the system in the center of mass reference frame, and the corresponding internal energy for method X, i.e., .

Image of FIG. 2.
FIG. 2.

Global minimum geometries for Ne n (n = 7, 8, 13, 14, 18, 19) on the classical pair potential surface.

Image of FIG. 3.
FIG. 3.

Classical and effective u eff (r jk ) pair potentials for Ne8 as a function of the total cluster energy. For E = −285.3 cm−1, u eff (r jk ) is also shown for selected iteration numbers.

Image of FIG. 4.
FIG. 4.

Top panel: Ne8 dissociation rates k diss (log scale) versus total energy E. Bottom panel: Same dissociation rates shown as a function of , the internal energy of Ne8 in each method. Rates in ps−1, energies in cm−1.

Image of FIG. 5.
FIG. 5.

Top panel: log10(k diss ) versus for Ne8, with being the maximum internal energy available for the daughter cluster Ne7. Bottom panel: log10(k diss ) versus for Ne8, with being the maximum internal energy available for the daughter cluster Ne7 for X = classical (black line, squares), ZPAD (red line, circles), or G-TDH (blue line, triangle), simulation method. Rates in ps−1, energies in cm−1.

Image of FIG. 6.
FIG. 6.

Capture probability P s (n, b, E, v p ) as a function of the impact parameter b for Ne8, computed using two different values of the cluster total energy, two projectile-target relative velocities and both classical (C) and ZPAD simulations. Average capture probabilities computed employing 2000 trajectories. A projectile was considered captured after the projection of its velocity on the line joining its center of mass with the cluster one had changed sign 5 times. Notice that both values of the cluster energy were sufficiently low to eliminate the chance for a dissociation event before a collision could take place.

Image of FIG. 7.
FIG. 7.

Capture probability P s (n, b, E, v p ) as a function of the impact parameter b for Ne8, computed using the G-TDH approach. Top panel: the width of the projectile was kept frozen at the value indicated in the picture, whereas the width of the cluster atoms is allowed to adapt. ZPAD results also shown for comparison. Bottom panel: G-TDH calculations employing a q value (see main text) for which the projectile width is activated in at least 90% of the trajectories. In all cases, E = −285.3 cm−1 and v = 4.17 bohrs ps−1.

Image of FIG. 8.
FIG. 8.

Capture probability P s (n, b, E, v p ) as a function of the impact parameter b for Ne8, computed using G-TDH with a dynamically adapting width for the projectile. Initially, α = 1.5 in all calculations; q was chosen to have more than 90% of trajectories activating width adaptation. Also shown, there are the results obtained by classical (C) and ZPAD trajectories. Top panel, E = 285.3 cm−1; bottom panel, E = −241.4 cm−1.

Tables

Generic image for table
Table I.

Global minimum potential (V min ), ground state energy obtained using DMC simulations (), the harmonic approximation (), and the G-TDH model () for Ne n species, in cm−1. The energy difference Δ0(n) for the Ne n → Ne n−1 + Ne process is shown in a few selected cases as obtained from the DMC, HA, and G-TDH results. (See Fig. 1 for energy definitions.)

Generic image for table
Table II.

Dissociation rate k diss for Ne8 as a function of the total energy of the cluster E as computed using classical, ZPAD, and G-TDH simulations. Also shown is the dissociation energy for the process Ne n → Ne n−1 + Ne as a function of E when both Ne8 and Ne7 are described by the effective potential u eff (r jk ) specifically optimized for Ne8 at its chosen energy. Energies in cm−1 and rates in ps−1. For the classical simulations, Δ0 = 93.71 cm−1.

Generic image for table
Table III.

Capture cross section σ(n, E int , v p ) (in bohr2) as a function of the cluster energy E (in cm−1) and the projectile speed v p (in bohr ps−1) for Ne8 computed using classical trajectories, ZPAD dynamics and G-TDH.

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/content/aip/journal/jcp/137/1/10.1063/1.4730033
2012-07-02
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Exploring the importance of quantum effects in nucleation: The archetypical Nen case
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/1/10.1063/1.4730033
10.1063/1.4730033
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