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Modeling the intrusion of molecules into graphite: Origin and shape of the barriers.

Huber SE, Probst M - Int J Mass Spectrom (2014)

Bottom Line: We compare the energy barriers encountered by these molecular projectiles with the ones that are obtained for atomic H, Be, C and O.The barriers are substantially lower if projectiles possess free valences that can bind to the carbon entity.Implications with respect to plasma-surface interaction are discussed.

View Article: PubMed Central - PubMed

Affiliation: Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria.

ABSTRACT

We performed density functional theory calculations to explore the energetic and geometric aspects of the permeation of H2, BeH x , OH x (x = 1, 2) and CH y (y = 1-4) through the central hexagon of coronene. Coronene serves as a cluster model for extended graphene which can be regarded as the first layer of a graphite (0 0 0 1) surface. We compare the energy barriers encountered by these molecular projectiles with the ones that are obtained for atomic H, Be, C and O. The barriers are substantially lower if projectiles possess free valences that can bind to the carbon entity. Furthermore, for some of the species fragmentation is observed. Implications with respect to plasma-surface interaction are discussed.

No MeSH data available.


Related in: MedlinePlus

Permeation mechanism of water through the center of coronene. H, C and O atoms are depicted as light blue, yellow and red spheres, respectively. Values for z are given in Å. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
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fig0030: Permeation mechanism of water through the center of coronene. H, C and O atoms are depicted as light blue, yellow and red spheres, respectively. Values for z are given in Å. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)

Mentions: For water as projectile, i.e. OH2, we note for z < 1.2 Å also a strongly enhanced repulsion, see Fig. 5(c). This can be expected from the closed-shell configuration of the water molecule. Beyond z = 1.2 Å, however, we observe a significant attractive contribution from ΔE indicating temporary bonding in the region between 1.4 and 2.0 Å. The mechanism underlying this feature is depicted in Fig. 6. At z = 1.2 Å the coronene is strongly distorted and repelled by the water molecule. At z = 1.4 Å, however, one of the H atoms (light blue sphere in Fig. 6) of the water molecule is donated to one of the carbon atoms (yellow spheres in Fig. 6) of the central hexagon of coronene. At z = 1.6 Å both of the hydrogen atoms have been donated and O (red sphere in Fig. 6) binds to two C atoms. This situation remains also for z = 1.8 Å. At z = 2.0 Å the departing O atom re-captures the two H atoms and a water molecule is formed again.


Modeling the intrusion of molecules into graphite: Origin and shape of the barriers.

Huber SE, Probst M - Int J Mass Spectrom (2014)

Permeation mechanism of water through the center of coronene. H, C and O atoms are depicted as light blue, yellow and red spheres, respectively. Values for z are given in Å. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4375830&req=5

fig0030: Permeation mechanism of water through the center of coronene. H, C and O atoms are depicted as light blue, yellow and red spheres, respectively. Values for z are given in Å. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
Mentions: For water as projectile, i.e. OH2, we note for z < 1.2 Å also a strongly enhanced repulsion, see Fig. 5(c). This can be expected from the closed-shell configuration of the water molecule. Beyond z = 1.2 Å, however, we observe a significant attractive contribution from ΔE indicating temporary bonding in the region between 1.4 and 2.0 Å. The mechanism underlying this feature is depicted in Fig. 6. At z = 1.2 Å the coronene is strongly distorted and repelled by the water molecule. At z = 1.4 Å, however, one of the H atoms (light blue sphere in Fig. 6) of the water molecule is donated to one of the carbon atoms (yellow spheres in Fig. 6) of the central hexagon of coronene. At z = 1.6 Å both of the hydrogen atoms have been donated and O (red sphere in Fig. 6) binds to two C atoms. This situation remains also for z = 1.8 Å. At z = 2.0 Å the departing O atom re-captures the two H atoms and a water molecule is formed again.

Bottom Line: We compare the energy barriers encountered by these molecular projectiles with the ones that are obtained for atomic H, Be, C and O.The barriers are substantially lower if projectiles possess free valences that can bind to the carbon entity.Implications with respect to plasma-surface interaction are discussed.

View Article: PubMed Central - PubMed

Affiliation: Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria.

ABSTRACT

We performed density functional theory calculations to explore the energetic and geometric aspects of the permeation of H2, BeH x , OH x (x = 1, 2) and CH y (y = 1-4) through the central hexagon of coronene. Coronene serves as a cluster model for extended graphene which can be regarded as the first layer of a graphite (0 0 0 1) surface. We compare the energy barriers encountered by these molecular projectiles with the ones that are obtained for atomic H, Be, C and O. The barriers are substantially lower if projectiles possess free valences that can bind to the carbon entity. Furthermore, for some of the species fragmentation is observed. Implications with respect to plasma-surface interaction are discussed.

No MeSH data available.


Related in: MedlinePlus