Displacive or Order-Disorder Phase Transition? The H-bond Dynamics in Multicaloric Ammonium Sulfate

Malec, Leszek M.; Brela, Mateusz Z.; Stadnicka, Katarzyna

doi:10.1016/j.actamat.2021.116782

Cited by 9 publications

(13 citation statements)

References 57 publications

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“…(5) The evolution of bonds and intermolecular distances, as already described for lattice parameters, did not show any discontinuity within the investigated pressure range. This was a definitively different behavior than that observed at low temperature by Malec et al [4,7], who, with a series of single crystal X-ray diffraction measurements in the temperature range of 273-163 K, showed a dynamical effect at the ferrielectric phase transition. A strong discontinuity in the evolution of tetrahedral bond lengths and angles, and in those intermolecular distances at 233 K, was described by Iqbal and Christoe [2].…”

Section: Discussioncontrasting

confidence: 64%

“…In addition, Iqbal and Christoe [2] showed that by decreasing temperature until the transition, not only the order-disorder of the NH 4 + group appears, but a decrease in the librations of the SO 4 ion coupled with a subtle distortion of the polyhedra through the enhancing hydrogen bond are also evident. Recently, Malec et al [4] studied the H-bond dynamic in mascagnite and confirmed the intermediate character between a displacive and an order-disorder phase transition. Using 14 N NMR spectra collected around 223 • C, Lim [5] showed that the phase transition was caused by the change of the 14 N environment in the NH 4 + groups, i.e., the temperature affects the degree of distortion of the tetrahedral H-N group, rather than the SO 4 group.…”

Section: Introductionmentioning

confidence: 91%

“…Recently, Malec et al [4] studied the H-bond dynamic in mascagnite and confirmed the intermediate character between a displacive and an order-disorder phase transition. Using 14 N NMR spectra collected around 223 • C, Lim [5] showed that the phase transition was caused by the change of the 14 N environment in the NH 4 + groups, i.e., the temperature affects the degree of distortion of the tetrahedral H-N group, rather than the SO 4 group. In one type of ammonium group, NH 4 (1), N-H decreases from 1.075 to 1.053 Å, whereas in NH 4 (2), N-H decreases from 1.062 to 1.048 Å. Mikhaleva [6] showed the effect of temperature and pressure on thermodynamic parameters and the hysteresis at the ferroelectric phase transition.…”

Section: Introductionmentioning

confidence: 91%

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High Pressure Behavior of Mascagnite from Single Crystal Synchrotron X-ray Diffraction Data

et al. 2021

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High-pressure synchrotron X-ray diffraction was carried out on a single crystal of mascagnite, compressed in a diamond anvil cell. The sample maintained its crystal structure up to ~18 GPa. The volume–pressure data were fitted by a third-order Birch–Murnaghan equation of state (BM3-EOS) yielding K0 = 20.4(7) GPa, K0′ = 6.1(2), and V0 = 499(1) Å3, as suggested by the F-f plot. The axial compressibilities, calculated with BM3-EOS, were K0a = 35(3), K’0a = 7.7(7), K0b = 10(3), K’0b = 7(1), K0c = 25(1), and K’0c = 4.3(2) The axial moduli measured using a BM2-EOS and fixing K’0 equal to 4, were K0a = 52(2), K0b = 20 (1), and K0c = 29.6(4) GPa, and the anisotropic ratio of K0a: K0b: K0c = 1: 0.4: 0.5. The evolution of crystal lattice and geometrical parameters indicated no phase transition until 17.6 GPa. Sulphate polyhedra were incompressible and the density increase of 30% compared to investigated pressure should be attributed to the reduction of weaker hydrogen bonds. In contrast, some of them, directed along [100], were very short at room temperature, below 2 Å, and showed a very low compressibility. This configuration explains the anisotropic compressional behavior and the lowest compressibility of the a axis.

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Section: Discussioncontrasting

confidence: 64%

Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 91%

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High Pressure Behavior of Mascagnite from Single Crystal Synchrotron X-ray Diffraction Data

et al. 2021

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“…H-bond parameters can successfully indicate the changes in relative positions and orientations of molecules during the simulation. As HB geometrical parameters store information about structure symmetry, they are great indicators of structure instability or disorder . HB lengths (HA) and donor–hydrogen···acceptor angles (DHA) were computed step by step for the entire trajectory for N–H···O and C–H···O contacts, which in the experimental crystal structure have HA ≤ 5.0 Å.…”

Section: Results and Discussionmentioning

confidence: 99%

“…As HB geometrical parameters store information about structure symmetry, they are great indicators of structure instability or disorder. 68 HB lengths (HA) and donor−hydrogen•••acceptor angles (DHA) were computed step by step for the entire trajectory for N−H•••O and C−H•••O contacts, which in the experimental crystal structure have HA ≤ 5.0 Å. Therefore, in the hypothetical case of system disruption, the contacts which would arise in the simulated structure according to some significant reorientation of the molecules can also be tracked.…”

Section: Analysis Of Bomd Simulated H-bondmentioning

confidence: 99%

Chasing the Co-crystal Disappearing Polymorph with Ab Initio Methods

Malec

Gryl

Oszajca

et al. 2021

Crystal Growth & Design

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Crystal polymorphism has a major impact on material properties such as thermal stability, bioavailability, and solubility. The application of co-crystals in the pharmaceutical industry requires polymorph screening to avoid unwanted phase transitions, which can cause property reduction. In this work, three polymorphs of urea−barbituric acid (1:1) co-crystals were investigated to describe the dynamic character of their H-bond networks and to explain the disappearance of the polar polymorph. For the studied polymorphs, Born−Oppenheimer molecular dynamics simulations were performed. Detailed analysis of hydrogen bonds and power spectra calculations were conducted using the obtained trajectories. The relative stability of each polymorph has been considered in terms of NVT and NVE ensembles. The results of computations were discussed in light of the analysis of H-bond propensities, coordination scores, and the obtained experimental data. To our knowledge, the polar form of urea−barbituric acid co-crystal can be called one of the first known examples of co-crystal disappearing polymorph.

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Origin of the Large Entropy Change in the Molecular Caloric and Ferroelectric Ammonium Sulfate

Yuan

Meijer

Cai

et al. 2022

Adv Funct Materials

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The deceptively simple inorganic salt ammonium sulfate undergoes a ferroelectric phase transition associated with a very large entropy change and both electrocaloric and barocaloric functionality. While the structural origins of the electrical polarisation are now well established, those of the entropy change have been controversial for over 50 years. This question is resolved here using a combination of density‐functional theory phonon calculations with inelastic neutron scattering under variable temperature and pressure, supported by complementary total and quasielastic neutron scattering experiments. A simple model of the entropy in which each molecular ion is disordered across the mirror plane in the high symmetry phase, although widely used in the literature, proves to be untenable. Instead, the entropy arises from low‐frequency librations of ammonium ions in this phase, with harmonic terms that are very small or even negative. These results suggest that, in the search for molecular materials with functionality derived from large entropy changes, vibrational entropy arising from broad energy minima is likely to be just as important as configurational entropy arising from crystallographic disorder.

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Displacive or Order-Disorder Phase Transition? The H-bond Dynamics in Multicaloric Ammonium Sulfate

Cited by 9 publications

References 57 publications

High Pressure Behavior of Mascagnite from Single Crystal Synchrotron X-ray Diffraction Data

High Pressure Behavior of Mascagnite from Single Crystal Synchrotron X-ray Diffraction Data

Chasing the Co-crystal Disappearing Polymorph with Ab Initio Methods

Origin of the Large Entropy Change in the Molecular Caloric and Ferroelectric Ammonium Sulfate

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