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Xe nuclear magnetic resonance line shapes in channels decorated with paramagnetic centers
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10.1063/1.2338809
/content/aip/journal/jcp/125/11/10.1063/1.2338809
http://aip.metastore.ingenta.com/content/aip/journal/jcp/125/11/10.1063/1.2338809

Figures

Image of FIG. 1.
FIG. 1.

The supercells constructed for model systems used in this work (the simulation box). All have the same paramagnet to framework atom ratio. The dark atoms are the C–C units in the original carbon nanotube which have been replaced by ; the dots are dummy atoms placed between nanotubes to prevent the Xe atoms from being created in interstitial positions. The lines delineate the unit cells. All views, except for model A are looking down the c axis of the crystal. The side view of model A shows the -doping pattern (one ring per unit cell). The four molecules are arranged in a ring so as to have the axis of the paramagnetic center parallel to the channel axis. All the models shown in this figure have the -doping pattern seen in the side view of model A, i.e., one ring per unit cell. Model B has the same arrangement, and the same distribution within the channel as in model A, but the distribution within the crystal is different from model A. Model C has the same distribution of paramagnetic centers as model B, but the axes of the paramagnetic centers are perpendicular to the channel axis. Model D channels have smaller diameter, and the same parallel orientation of paramagnetic centers as model B; there are three molecules arranged in a ring. Model H channels have larger diameters, and the same parallel orientation of paramagnetic centers as model B; there are five molecules arranged in a ring.

Image of FIG. 2.
FIG. 2.

The supercells for the model systems which have twice the concentration of paramagnetic centers compared to corresponding models in Fig. 1. All have four molecules arranged in a ring. Model E has the same parallel arrangement of paramagnetic centers as model B, with the four molecules stacked vertically every level rather than every other level. Model F has the same parallel arrangement of paramagnetic centers as model E, but the positions of the four units rotate at each level producing a helical pattern. Model G has the same perpendicular orientation of paramagnetic centers as model C.

Image of FIG. 3.
FIG. 3.

The Xe line shapes for Xe-channel interactions (in the limit of zero Xe occupancy) at 300, 250, and in the neon nanotube doped with in model B (bottom) compared with the Xe line shapes under the same conditions, but with the coefficients of all hyperfine terms zeroed out, i.e., in the absence of hyperfine effects (top).

Image of FIG. 4.
FIG. 4.

The effect of concentration and the distribution of paramagnetic centers. (a) Xe line shapes for Xe-channel interactions (in the limit of zero Xe occupancy) at 300, 250, and in the neon nanotube doped with in model E (top) which has twice the concentration of paramagnetic centers as model B in Fig. 3. (b) Xe line shapes in model A (bottom) which have the same concentration and arrangement of paramagnetic centers within the channel as model B in Fig. 3, but the distribution of paramagnets in the solid is different.

Image of FIG. 5.
FIG. 5.

The axis of the paramagnetic center is perpendicular to the axis of the channel. Line shapes in model C (top) are compared with line shapes in model G which has twice the concentration of paramagnetic centers (bottom).

Image of FIG. 6.
FIG. 6.

The Xe line shapes as a function of Xe occupancy. Xe line shapes in the neon nanotube doped with in model B at (right) are compared with the line shapes under the same conditions, but with the coefficients of all hyperfine terms zeroed out, i.e., in the absence of hyperfine effects (left). The fractional occupancy .

Image of FIG. 7.
FIG. 7.

The effect of the channel diameter. The Xe line shapes for Xe-channel interactions (in the limit of zero Xe occupancy) are compared in the -doped neon nanotubes of increasing diameter in models H, B, and D at 300 (top) and at (bottom).

Tables

Generic image for table
Table I.

The hyperfine contributions to the Xe chemical shift tensor in each of the model systems.

Generic image for table
Table II.

The Fermi contact contributions to the isotropic Xe chemical shift in each of the model systems.

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/content/aip/journal/jcp/125/11/10.1063/1.2338809
2006-09-20
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Xe nuclear magnetic resonance line shapes in channels decorated with paramagnetic centers
http://aip.metastore.ingenta.com/content/aip/journal/jcp/125/11/10.1063/1.2338809
10.1063/1.2338809
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