Anomalous thermoelastic behaviour of orientationally disordered (NH4I)x(KI)1−x mixed crystals

Tiwari, Alpana; Singh, Rajendra

doi:10.1016/j.jpcs.2010.01.004

Cited by 4 publications

(3 citation statements)

References 37 publications

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“…MacDonald used the term “mixed crystals” to describe these materials. This term has since been used extensively in the literature to describe a variety of types of materials, from simple salts, − through doped polyoxometallates, − to crystals containing similar discrete molecules or ions in similar ratios that co-crystallize in a single lattice. ,− To avoid confusion, we prefer to use the terms “co-crystal” to describe crystals with multiple molecular components and “molecular alloy” to refer specifically to the case where the molecular components are interchangeable. − …”

Section: Introductionmentioning

confidence: 99%

Supramolecular Selection in Molecular Alloys

Bouzaid

Schultz

Lao

et al. 2012

Crystal Growth & Design

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Complexes of the type [M(phen)3](PF6)2 (M = Ni(II), Fe(II), Ru(II) and phen = 1,10-phenanthroline) were found to co-crystallize to form molecular alloys (solid solutions of molecules) with general formula [MA x MB 1–x (phen)3](PF6)2·0.5H2O in which the relative concentrations of the metal complexes in the crystals closely match those in the crystallizing solution. Consequently, the composition of the co-crystals can be accurately predicted and controlled by modulating the relative concentrations of the metal complexes in the crystallizing solution. Although they are chemically and structurally similar, complexes of the type [M(bipy)3](PF6)2 (M = Ni(II), Fe(II), Ru(II) and bipy = 2,2′-bipyridine) display markedly different behavior upon co-crystallization. In this case, the resulting co-crystals of general formula [MA x MB 1–x (bipy)3](PF6)2 have relative concentrations of the constituent complexes that are markedly different from the relative concentrations of the complexes initially present in the crystallizing solution. For example, when the nickel and iron complexes are co-crystallized from a solution containing a 50:50 ratio of each, the result is the formation of some crystals with a higher proportion of iron and others with a higher proportion of nickel. The relative concentrations of the metal complexes in the crystals can vary from those in the crystallizing solutions by as much as 15%. This result was observed for a range of combinations of metal complexes (Ni/Fe, Ni/Ru, and Fe/Ru) and a range of starting concentrations in the crystallizing solutions (90:10 through to 10:90 in 10% increments). To explain this remarkable result, we introduce the concept of “supramolecular selection”, which is a process driven by molecular recognition that leads to the partially selective aggregation of like molecules during crystallization.

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Section: Introductionmentioning

confidence: 99%

Supramolecular Selection in Molecular Alloys

Bouzaid

Schultz

Lao

et al. 2012

Crystal Growth & Design

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“…A series of pure and mixed crystals have been studied by several researchers with the aim of identifying new materials [8][9][10]. Electrical, dielectrical, and micro-hardness studies on mixed crystals of alkali and alkaline earth halides, such as KCl -NaCl, KBr -KI, KCl -KBr, KBr -NaI, AgBr -AgCl, and CaF2 -SrF2 have been reported extensively [11][12][13][14]. A normal Na + ionic conductor, NaNO3 has been chosen and an attempt has been made to improve the conductivity by mixing with Sr(NO3)2, another solid ionic conductor, heterogeneously.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Pure and L-Proline Doped Potassium Nitrate and Sodium Nitrate Crystals

Velumani¹,

Paul

Haris

et al. 2022

Trends Sci

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The crystals of pure and L-Proline doped Potassium nitrate and Sodium nitrate were grown in solution by slow evaporation technique using supersaturated solution of the salts. Characterization studies of the crystals have been done to find the impact of the L-Proline on the regular lattice arrangement of the pure crystal. The Powder XRD spectrum reveals that the pure and doped KNO3 crystals belong to orthorhombic structure; and pure and doped NaNO3 are rhombohedral in nature. This is a unit cell with parameters a = b = c; α = β = γ ≠ 90°. There are small changes in the unit cell dimensions but the structure of the pure and doped crystals remain to be orthorhombic in nature. The FTIR spectrum shows the functional group analysis of the samples. The various decomposition process of the crystals with respect to temperature have been carried out in thermal analysis. The dielectric properties exhibit the variation of dielectric constant, and capacitance with frequency at various temperatures for pure and doped crystals. The doped crystals found to have considerable effect on the optical, thermal and dielectric properties. HIGHLIGHTS Effect of dopant L-Proline on the growth of Potassium nitrate and Sodium nitrate crystals by solution growth was carried out for the first time The studies based on dielectric properties and thermal analysis gives a broad understanding about the influence of the dopant on the pure crystals Variation of dielectric constant, resistance, and capacitance with respect to frequency at various temperatures reveals that the dopant L-Proline has a significant effect GRAPHICAL ABSTRACT

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“…It has been applied successfully by Gaur et.al. and others to explain the elastic, thermal and dynamical properties of the orientationally disordered alkali cyanides, their mixed crystal counterparts, sodium superoxide, ammonium halides and ammonium-alkali halide mixed crystals [10][11][12][13][14][15][16][17][18][19][20]. The present theoretical approach is motivated from the versatility and considerable success of the ETSM, we have thought it pertinent to apply this ETSM to investigate the temperature dependence of the second order elastic constants of (NH 4 I) x (KI) 1-x .…”

Section: Introductionmentioning

confidence: 99%

Temperature Dependence of Second and Higher Order Elastic Constants of Orientationally Disordered (NH4I)x (KI)1-x Mixed Crystals

Tiwari¹

2014

AMR

Self Cite

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We have incorporated the translational rotational (TR) coupling effects in the framework of three body force shell model (TSM) to develop an extended TSM (ETSM). This ETSM has been applied to reveal the second order elastic constants (C11, C12and C44) in the dilute regimes 0≤ x ≤ 0.50 as a function of temperature for 10K≤T≤300K. The anomalous elastic behaviour in C44below 100 K has been depicted well by ETSM results in the orientationally disordered (NH4I)x(KI)1-xmixed crystals. In order to present a visual comparison of the TR-coupling effect on second order elastic constants, we have evaluated the SOECs with and without TR coupling term in ETSM. Besides third order elastic constants have also been studied and discussed for concentration range 0≤x≤0.50 as a function of temperature for 10K≤T≤300K.

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Anomalous thermoelastic behaviour of orientationally disordered (NH4I)x(KI)1−x mixed crystals

Cited by 4 publications

References 37 publications

Supramolecular Selection in Molecular Alloys

Supramolecular Selection in Molecular Alloys

Characterization of Pure and L-Proline Doped Potassium Nitrate and Sodium Nitrate Crystals

Temperature Dependence of Second and Higher Order Elastic Constants of Orientationally Disordered (NH<sub>4</sub>I)<sub>x </sub>(KI)<sub>1-x </sub>Mixed Crystals

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