Some interesting phase transitions in solids

Rao, C. N. R.

doi:10.1007/bf02908483

Cited by 5 publications

(4 citation statements)

References 34 publications

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“…The peak temperatures T max (∼182 K for 1 and 154 K for 2 ) are close to the results from the magnetic susceptibility measurements. The endothermic enthalpy changes (Δ H ), which were calculated from the integrated peak areas, are estimated to be 316.6 J·mol −1 for 1 and 1082.1 J·mol −1 for 2 , confirming that the transitions are first-order. − Compared with 1 , compound 2 shows a larger endothermic enthalpy change. This observation is probably related to the strong H-bonding interactions in 2 , and the larger enthalpy change is essential contribution of lattice degrees of freedom in the transition of 2 .…”

Section: Resultsmentioning

confidence: 83%

Two Spin-Peierls-like Compounds Exhibiting Divergent Structural Features, Lattice Compression, and Expansion in the Low- Temperature Phase

et al. 2009

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Two quasi-one-dimensional (quasi-1D) compounds, [4'-CH(3)Bz-4-RPy][Ni(mnt)(2)] (mnt(2-) = maleonitriledithiolate), where 4'-CH(3)Bz-4-RPy(+) = 1-(4'-methylbenzyl)pyridinium (denoted as compound 1) and 1-(4'-methylbenzyl)-4-aminopyridinium (denoted as compound 2), show a spin-Peierls-like transition with T(C) approximately 182 K for 1 and T(C) approximately 155 K for 2. The enthalpy changes for the transition are estimated to be DeltaH = 316.6 J.mol(-1) for 1 and 1082.1 J.mol(-1) for 2. From fits to the magnetic susceptibility, the magnetic exchange constants in the gapless state are calculated to be J = 166(2) K with g = 2.020(23) for 1 versus J = 42(0) K with g = 2.056(5) for 2. In the high-temperature (HT) phase, 1 and 2 are isostructural and crystallize in the monoclinic space group P2(1)/c. The nonmagnetic cations and paramagnetic anions form segregated columns with regular anionic and cationic stacks. In the low-temperature (LT) phase, the crystals of the two compounds undergo a transformation to the triclinic space group P-1, and both anionic and cationic stacks dimerize. In the transformation from the HT to LT phases, the two compounds exhibit divergent structural features, with lattice compression for 1 but lattice expansion for 2, due to intermolecular slippage. Combined with our previous studies, it is also noted that the transition temperature, T(C), is qualitatively related to the cell volume in the HT phase for the series of compounds [1-(4'-R-benzylpyridinium][Ni(mnt)(2)] (where R represents the substituent). When there is a single substituent in the para position of benzene, giving a larger cell volume, the transition temperature increases.

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Section: Resultsmentioning

confidence: 83%

Two Spin-Peierls-like Compounds Exhibiting Divergent Structural Features, Lattice Compression, and Expansion in the Low- Temperature Phase

et al. 2009

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“…In the limiting case, both l 0 (¼TÁDS) and De approaches zero, and dr=dT will have 0=0 type indeterminacy like those in second order PT. 27,30 In such nano-scale, the classical Clausius-Clapeyron equation derived for the firstorder PT loses its physical meaning and breaks down in predicting the observed decrease in dr=dT (see Fig. 5(b)).…”

Section: 2mentioning

confidence: 99%

Stress hysteresis and temperature dependence of phase transition stress in nanostructured NiTi—Effects of grain size

Ahadi¹,

Sun²

2013

Appl. Phys. Lett.

229

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“…However, solid-solid nucleation/phase-transitions are often characterized as rare events, meaning required simulation times may go beyond the capabilities of the current computational architecture. To overcome this problem, we take inspiration from earlier computer simulations of polytypes 20,61 and explore the potential energy surface by altering potential energy surface. [62][63][64][65][66][67] All simulation details are provided in the supplementary information.…”

Section: δ To α-Phase Transition Of Fapbimentioning

confidence: 99%

“…This is mainly due to the lack of understanding and control over their synthesis process where one of the critical challenges is to eliminate the formation of hexagonal face-sharing structures and their alternative polytypes. [17][18][19][20][21][22][23][24][25] Therefore, it is necessary to study their formation process which can help to make reproducible and stable FAPbI 3 based PSCs. The temporal and spatial resolution required to study the dynamical process of crystallization: limit the usage of current state-of-the-art experimental techniques and a huge challenge to design and perform experiments for these materials.…”

Section: Introductionmentioning

confidence: 99%