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Characterization of Lewis acid sites on the (100) surface of : Ab initio calculations of adsorption
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10.1063/1.2933523
/content/aip/journal/jcp/128/22/10.1063/1.2933523
http://aip.metastore.ingenta.com/content/aip/journal/jcp/128/22/10.1063/1.2933523

Figures

Image of FIG. 1.
FIG. 1.

A side view (left) and a plan view (right) of the relaxed (100) T1 termination. The Al ions are represented by small spheres and the F ions by large spheres.

Image of FIG. 2.
FIG. 2.

Adsorption of above undercoordinated Al ions on the (100) T1 termination. (a) Adsorption on T1A sites. (b) Adsorption on T1B sites. (c) Adsorption on T1A and T1B sites.

Image of FIG. 3.
FIG. 3.

A plan view of adsorption on the (100) T1 termination at full monolayer coverage. There are two adsorbed molecules per unit cell. The channels in the bulk material are parallel to the ⟨001⟩ direction.

Image of FIG. 4.
FIG. 4.

The (100) T6 termination. can either bind to the surface Al ions from above (on T6A sites) or below (on T6B sites).

Image of FIG. 5.
FIG. 5.

Adsorption of above undercoordinated Al ions on the (100) T6 termination. (a) Adsorption on T6A sites. (b) Adsorption on T6B sites. (c) Adsorption on T6A and T6B sites.

Image of FIG. 6.
FIG. 6.

A plan view of adsorption on the (100) T6 termination at full monolayer coverage. There are four molecules adsorbed per unit cell. Arrows point to the five nearest neighbors of T6A and T6B sites. The neighboring adsorption sites for a molecule adsorbed to a T1A (T6B) site are labeled as (I) nearby T6A (T6B) site, (II) adjacent T6B (T6A) site, and (III) T6B (T6A) site across the channel. The channels in the bulk material are parallel to the ⟨001⟩ direction.

Image of FIG. 7.
FIG. 7.

The TPD curves obtained from lattice Monte Carlo simulations parametrized from the DFT BEs.

Image of FIG. 8.
FIG. 8.

The TPD curves obtained by Murthy et al. (Left) The three experimental results were obtained from different samples. Experiment A used untreated , experiment B used a sample that was first fluorinated using , and in experiment C, the sample was fluorinated using . The fluorination process is used to reverse surface hydrolysis. (Right) This graph is identical to the one on the left but also includes the results obtained from our lattice Monte Carlo simulations, shifted by to higher temperatures.

Tables

Generic image for table
Table I.

The basis sets used for nitrogen and hydrogen.

Generic image for table
Table II.

BEs, in eV per molecule, of as a function of the occuation of neighboring and nnn sites. Nearest neighbor sites are of an opposite site type while nnn sites are of the same type.

Generic image for table
Table III.

BEs of adsorbed to the T6 termination as a function of the occupancy of the its nearest neighbor sites. The nearest neighbor sites are described in detail in Sec. III B and shown diagrammatically in Fig. 6.

Generic image for table
Table IV.

The Mulliken charges, in , on the different surface species at full monolayer coverage after correction for BSSE. The changes in the charges are given with respect to the clean surface and an isolated molecule. An isolated molecule has a charge of on the nitrogen and of on the hydrogens.

Generic image for table
Table V.

Estimations of the electrostatic integration energy between the T1 termination and adsorbed molecules. The calculated BEs are given for comparison.

Generic image for table
Table VI.

Estimations of the electrostatic interaction energy between the T6 termination and adsorbed molecules. The calculated BEs are given for comparison.

Generic image for table
Table VII.

Estimation of the repulsive dipole interaction energy between neighboring molecules in the absence of the surface. The termination and adsorption sites describe the positioning of the molecules. The interaction energy includes the interactions from both nearest neighbors.

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/content/aip/journal/jcp/128/22/10.1063/1.2933523
2008-06-11
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Characterization of Lewis acid sites on the (100) surface of β-AlF3: Ab initio calculations of NH3 adsorption
http://aip.metastore.ingenta.com/content/aip/journal/jcp/128/22/10.1063/1.2933523
10.1063/1.2933523
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