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Parametrization of a reactive force field for aluminum hydride
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10.1063/1.3182853
/content/aip/journal/jcp/131/4/10.1063/1.3182853
http://aip.metastore.ingenta.com/content/aip/journal/jcp/131/4/10.1063/1.3182853

Figures

Image of FIG. 1.
FIG. 1.

(a) Bond dissociation profile of . REAXFF gives an equilibrium bond length of 1.6 Å. This is in excellent agreement with DFT value of 1.59 Å. (b) H–Al–H angle bend in molecule. The energies are computed with reference to the equilibrium angle energy.

Image of FIG. 2.
FIG. 2.

Small representative , , clusters used in the training set of REAXFF.

Image of FIG. 3.
FIG. 3.

The various polymorphic modifications of illustrated by the connection of the octahedra and channels through the polymorphs.

Image of FIG. 4.
FIG. 4.

EoSs for phases (DFT values are drawn using straight lines while those for REAXFF are drawn using dotted lines).

Image of FIG. 5.
FIG. 5.

(i) Dissociation profile of as calculated by DFT using nudged elastic band method. (ii) The energy profile during a MD simulation of a heating run of . The temperature was ramped up at a rate of 0.000 25 K/iteration.

Image of FIG. 6.
FIG. 6.

Illustrations of the atomic configurations and energy profiles for (a) alane dimerization reaction and (b) agglomeration of molecules.

Image of FIG. 7.
FIG. 7.

Snapshots of the clusters at the (a) beginning and (b) end of the simulation.

Image of FIG. 8.
FIG. 8.

(a) The completely agglomerated clusters at a temperature of 800 K. No molecular hydrogen was desorbed at this temperature. (b) The Al–Al pair distribution function of the cooled agglomerated clusters. The agglomerate was annealed to 0 K at a rate of 0.0025 K/iteration.

Image of FIG. 9.
FIG. 9.

The charge distribution plots of the alane clusters (0 ps) at the beginning of the simulation and (500 ps) that of the agglomerated cluster at the end of the simulation run.

Image of FIG. 10.
FIG. 10.

Desorption energy as a function of number of molecules abstracted from the system. The reference energy, shown by the dotted line, is the energy for .

Image of FIG. 11.
FIG. 11.

Geometries of the annealed clusters of , , , and . In the hydrogen deficient cluster the hydrogen atoms prefer to occupy surface sites rather than bulk.

Image of FIG. 12.
FIG. 12.

Charge distribution plots showing the transfer of charge during abstraction process of molecular hydrogen from cluster. The hydrogen atoms are negatively charged.

Image of FIG. 13.
FIG. 13.

The arrow shows a hydrogen molecule trapped in channel.

Tables

Generic image for table
Table I.

Bond energy and bond-order parameters. is in kcal/mol.

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Table II.

Atom parameters ( is in kcal/mol).

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Table III.

Coulomb parameters.

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Table IV.

Valence angle parameters.

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Table V.

Adsorption energies of hydrogen atoms on the high symmetry sites on Al(111) surface. The energies are in kcal/mol per H.

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Table VI.

Binding energies of , , and on Al(111) surface.

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Table VII.

Binding energies BEs (in kcal/mol ) of small clusters used in the training set.

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Table VIII.

Comparison between DFT and binding energies BEs of Kawamura et al. (in kcal/mol H) of small clusters.

Generic image for table
Table IX.

Relative stability of three phases with respect to the phase using the PAW and US-PP and REAXFF. The units are in kcal/mol.

Generic image for table
Table X.

The temperature at which molecular hydrogen is released from cluster. As the size of the cluster increases the temperature at which molecular hydrogen is released from the cluster also decreases.

Generic image for table
Table XI.

The heat of fragmentation of into various clusters during thermal heating of the cluster. The DFT values were computed using VASP at the PW91 level of theory. The energies are in kcal/mol.

Generic image for table
Table XII.

The energy of agglomeration (per ) of various small clusters of the series as calculated using DFT and REAXFF.

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/content/aip/journal/jcp/131/4/10.1063/1.3182853
2009-07-22
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Parametrization of a reactive force field for aluminum hydride
http://aip.metastore.ingenta.com/content/aip/journal/jcp/131/4/10.1063/1.3182853
10.1063/1.3182853
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