Structure analysis of the disordered cubic phase of rubidium cyanide

Ehrhardt, K.; Press, W.; Heger, G.

doi:10.1107/s0108768183002244

Cited by 23 publications

(4 citation statements)

References 2 publications

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“…The situation is similar to that for alkali metal cyanides, 15 for which extensive single-crystal neutron diffraction experiments have been carried out to investigate the disorder of the CN dumbbells in the high-temperature modifications. [16][17][18] The experimental findings rule out a free rotation (Pauling model), as reflections with equal (h 2 þ k 2 þ l 2 ), but different (hkl) have significantly different structure factors. Surprisingly, for the different alkali cyanides, pronounced differences in the preferred orientations of the CN dumbbells are found: whereas in NaCN 17 the maximum probability for the orientation of the CN dumbbells is along [100], in KCN (ref.…”

Section: Introductionmentioning

confidence: 94%

Phase transition in K₂C₂as studied by synchrotron X-ray powder diffraction and solid-state¹³C NMR spectroscopy

Zibrowius

Bähtz

Knapp

et al. 2004

Phys. Chem. Chem. Phys.

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Section: Introductionmentioning

confidence: 94%

Phase transition in K₂C₂as studied by synchrotron X-ray powder diffraction and solid-state¹³C NMR spectroscopy

Zibrowius

Bähtz

Knapp

et al. 2004

Phys. Chem. Chem. Phys.

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“…The Boltzmann distribution holds for the state in equilibrium, but in the following we assume that in the ordering process the relative values of w2, w,, ... we are determined by (18). This will be a little bit more accurate than what is given by (17), which corresponds to a completely random distribution.…”

Section: The Distribution Of Dipolesmentioning

confidence: 99%

Theoretical Investigation of Ferroelastic Phase Transition of Pure and Mixed Alkali Cyanide Systems by the Elastic Dipole Model. I. The Cubic‐Orthorhombic Phase Transition of Pure Potassium Cyanide

Yang

Lüty

1989

Physica Status Solidi (b)

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The kinetics of elastic ordering of KCR controlled by a thermally activated process is studied by considering the interaction between elastic CN-dipoles. The lattice constants obtained and reorientational activation energy of dipoles in the elastically ordered lattice agree quantitatively with experiments. The calculation indicates that the orientation ordering of elastic dipoles is induced by the strain field due to ordering alignment of dipoles. The elastic interaction between close neighbors of dipoles has little influence. The first-order character of the phase transition is obtained, and it is found that an initial degree of order depending on the temperature is necessary to start the ordering process. It is concluded that this corresponds to the nucleation process of the first-order phase transition.La cinetique de rearrangement 6lastique de KCN controlbe par un processus de thermoactivation est Btudike en considerant l'interaction entre les dipdles blastiques CN-. Les constantes du reseau obtenues et 1'6nergie d'activation de la reorientation des dipBles dans le reseau 6lastique ordonne sont en accord quantitatif avec les experiences. Le calcul indique que la reorientation des dipdles hlastiques est induite par le champ principal du aux dip8les realignes. L'interaction Blastique entre les proches voisins des dip6les a peu d'influence. Le caractere de premier ordre de la transition de phase a At6 obtenu et nous trouvons qu'un degre initial d'ordre dependant de la temperature est necessaire pour demarrer le processus de rearrangement. Nous concluons que cela correspond a un processus de nucleation de la transition de phase du premier ordre. l ) Nanjing, People's Republic of China. ?) Salt Lake City, UT 84112, USA.

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“…An investigation [9] by neutron diffraction indicated that the CNions in the disordered cubic phase of RbCN have a higher orientation probability in the direction [ l l l ] , but the distribution is more spherical near T, than far above it.…”

Section: Zhengjtj Yang and F Lutymentioning

confidence: 99%

“…A firstorder phase transition takes place in RbCN, too. Again, if the curve which has the X-axis as its tangent is assumed to be the phase transition curve corresponding to 132 K (in fact, it corresponds to the overheated curve as discussed inI), we obtained the permanent dipole moment indirection [I, 12,6] in RbCN as pY1 = 2.92 x 10-2ONm (9) and the order parameter a t the phase transition point as S , = 0.74.…”

Section: The Pvocess Of the Phase Transitionmentioning

confidence: 99%

Theoretical Investigation of Ferroelastic Phase Transition of Pure and Mixed Alkali Cyanide Systems by the Elastic Dipole Model. II. The Cubic–Monoclinic Phase Transition of Pure Rubidium Cyanide

Yang

Lüty

1989

Physica Status Solidi (b)

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The cubic-monoclinic structural phase transition of RbCN is investigated with the elastic dipole model. The calculation shows that the monoclinic structure of RbCN consists of two groups of dipoles of equal number but aligning in two different orientations, which are obtained from the strain of the unit cell in agreement with the experiments. A stable configuration of the two groups of dipoles is proposed. The alternate displacement of the cations calculated from this configuration agrees with the experiment in direction but is too large in magnitude due to the elastic continuum model used. The interaction between neighboring dipoles is the main part of the ordering energy in contrast to the ferroelastic case of KCN. I n fact a new kind of ordering transitionantiferroelastic phasc transitionis proposed for RbCN.La transition de phase structurelle cubique-monoclinique de RbCN est recherch6e avec le modhle du dipole Blastique. Le calcul montre que la structure monoclinique de RbCN se compose de deux groupes de dipoles en nombre Bgal, mais align& dans deux directions diff6rentes lesquels sont obtenus A partir de la contrainte de la cellule unit6 en accord avec l'exphrience. Une configuration stable de deux groupes de dipoles est propos6e. Le dkplacement alternatif de cations calculB iL partir de cette configuration est en accord avec l'exphrience en direction, mais est trop grand en amplitude A cause de l'utilisation de modde d u continuum Blastique. L'interaction entre dipoles voisins est la part principale de 1'Bnergie de r6arrangement en contraste avec le cas ferroklastique de KCK.Une nouvelle sorte de transition de &arrangementtransition de phase anti-ferrohlastiqueest proposBe pour RbCN.

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Structure analysis of the disordered cubic phase of rubidium cyanide

Cited by 23 publications

References 2 publications

Phase transition in K₂C₂as studied by synchrotron X-ray powder diffraction and solid-state¹³C NMR spectroscopy

Phase transition in K₂C₂as studied by synchrotron X-ray powder diffraction and solid-state¹³C NMR spectroscopy

Theoretical Investigation of Ferroelastic Phase Transition of Pure and Mixed Alkali Cyanide Systems by the Elastic Dipole Model. I. The Cubic‐Orthorhombic Phase Transition of Pure Potassium Cyanide

Theoretical Investigation of Ferroelastic Phase Transition of Pure and Mixed Alkali Cyanide Systems by the Elastic Dipole Model. II. The Cubic–Monoclinic Phase Transition of Pure Rubidium Cyanide

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Structure analysis of the disordered cubic phase of rubidium cyanide

Cited by 23 publications

References 2 publications

Phase transition in K2C2as studied by synchrotron X-ray powder diffraction and solid-state13C NMR spectroscopy

Phase transition in K2C2as studied by synchrotron X-ray powder diffraction and solid-state13C NMR spectroscopy

Theoretical Investigation of Ferroelastic Phase Transition of Pure and Mixed Alkali Cyanide Systems by the Elastic Dipole Model. I. The Cubic‐Orthorhombic Phase Transition of Pure Potassium Cyanide

Theoretical Investigation of Ferroelastic Phase Transition of Pure and Mixed Alkali Cyanide Systems by the Elastic Dipole Model. II. The Cubic–Monoclinic Phase Transition of Pure Rubidium Cyanide

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Phase transition in K₂C₂as studied by synchrotron X-ray powder diffraction and solid-state¹³C NMR spectroscopy

Phase transition in K₂C₂as studied by synchrotron X-ray powder diffraction and solid-state¹³C NMR spectroscopy