Order–Disorder Transformation in Potassium Graphite

Parry, G.; Nixon, D E

doi:10.1038/216909a0

Cited by 76 publications

(12 citation statements)

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“…Modifications of the selection rules of the hk.l lines were also observed on KC24 and RbC24 similar to those on CSC24 (Rousseaux et al, 1990;Parry & Nixon, 1967). The contradiction reported by Rousseaux et al (1990) about the thermal evolution of the selection rules could then be explained by a transition between two stackings similar to those described in this paper.…”

Section: Evolution Of the Stackingsupporting

confidence: 86%

“…The c~flF sequence could also be described in terms of successive in-plane translations from one layer to the next, where the translation is randomly chosen among vectors close to (1/3a,2/3b) and (2/3a,1/3b), the extremities of the translation vectors being in register with the graphite honeycomb on either side of the Cs layer. The similarities between the a and F layers and the preferential atomic positions of each layer show that the initial stacking can be described by a two-layer pseudohexagonal model, as previously suggested by Parry & Nixon (1967) and Rousseaux et al (1990). Though other combinations with different possible translations between a, fl and F layers (commensurate translations with the rhombohedral graphite) were examined, the best agreement was obtained with the pseudohexagonal two-layer model; the 10.l selection rules along the c* axis were well reproduced by the intensity calculations (Fig.…”

Section: Initial Stackingsupporting

confidence: 72%

“…2) coexists with the rhombohedral stacking at a lower temperature. Rousseaux et al (1990) and Parry & Nixon (1967) observed the same selection rules in the case of KC24 and suggested that the periodicity along the c axis is twice that of graphite (c = 6Ic). They proposed the sequence, ot1AB/31BCot2CAfl2ABa3BCfl3CAOtl but they did not indicate the translation vectors between the alkali layers.…”

Section: Initial Stackingmentioning

confidence: 68%

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The Low-Temperature Three-Dimensional Structures of the Second-Stage Caesium Graphitide

Duclaux¹,

Rannou²,

Lelaurain³

et al. 1998

J Appl Cryst

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The three‐dimensional (3D) structure of the second‐stage CSC24 graphitide was investigated by recording hk.l monochromatic rotating‐crystal diffractograms. At low temperature, the two‐dimensional (2D) structure is formed of an incommensurate (2.53 x 2.53 R 14.5°) and a commensurate (2 x 2 R 0°) lattice. Below 140 K, whereas the Cs incommensurate layers become 3D ordered, the 2 x 2 R 0° commensurate layers are randomly distributed in the structure. The commensurate structure, with composition CsC16 (stage two), probably equilibrates the lack of Cs induced by the incommensurate structure (composition CSC26), in order to reach the global composition CSC24 of the compound. Depending on the temperature, two kinds of stackings appear. Below 140 K, the incommensurate Cs layers are arranged in a 2D‐modulated initial stacking, transformed at a lower temperature into a rhombohedral stacking in which Cs atoms are modulated along the c axis. Simulation of the selection rules allowed the determination of models of the incommensurate layers stacking along the c axis, with translations from one Cs layer to another layer commensurate with the graphite lattice. The initial stacking is described by a pseudo‐two‐layer model with successive random translations and a short‐range order. The structure appearing at a lower temperature is described by a pseudorhombohedral stacking with definite translations. The transition from the initial stacking with a first‐neighbour interaction to the pseudorhombohedral stacking with a second‐neighbour interaction could be a result of the change in interactions between the Cs atoms and the graphitic host, due to the dominating influence of the graphite periodic potential at low temperature.

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Section: Evolution Of the Stackingsupporting

confidence: 86%

Section: Initial Stackingsupporting

confidence: 72%

Section: Initial Stackingmentioning

confidence: 68%

See 1 more Smart Citation

The Low-Temperature Three-Dimensional Structures of the Second-Stage Caesium Graphitide

Duclaux¹,

Rannou²,

Lelaurain³

et al. 1998

J Appl Cryst

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show abstract

“…These measurements were limited to rates under 10 4 s" 1 temperature readout and control were accurate to a few millidegrees Kelvin. More experimental details are given in I.…”

mentioning

confidence: 99%

Island Growth and Orientational Locking of Potassium Intercalated in Graphite

et al. 1980

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“…Upon intercalation of the graphite with the alkali metals to stage 2, as in C24Rb, the stacking sequence is converted to A/AB/BC/CA/A... (Parry, Nixon, Lester & Levene, 1969;Parry & Nixon, 1967;Nixon & Parry, 1968) in which A refers, as above, to graphite and the slashed line (/) refers to a layer of disordered or liquid-like alkali metal. The stage index refers to the number of carbon layers separating intercalate layers.…”

Section: Introductionmentioning

confidence: 99%