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A Chemical-Pressure-Induced Phase Transition Controlled by Lone Electron Pair Activity.

ABSTRACT: The chemical pressure approach offers a new paradigm for property control in functional materials. In this work, we disclose a correlation between the β → α pressure-induced phase transition in SnMoO₄ and the substitution process of Mo⁶⁺ by W⁶⁺ in SnMo_1-xW_xO₄ solid solutions (x = 0-1). Special attention is paid to discriminating the role of the lone pair Sn²⁺ cation from the structural distortive effect along the Mo/W substitution process, which is crucial to disentangle the driven force of the transition phase. Furthermore, the reverse α → β transition observed at high temperature in SnWO₄ is rationalized on the same basis as a negative pressure effect associated with a decreasing of W⁶⁺ percentage in the solid solution. This work opens a versatile chemical approach in which the types of interactions along the formation of solid solutions are clearly differentiated and can also be used to tune their properties, providing opportunities for the development of new materials.

SUBMITTER: Gomes EO

PROVIDER: S-EPMC9619963 | biostudies-literature | 2022 Oct

REPOSITORIES: biostudies-literature

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A Chemical-Pressure-Induced Phase Transition Controlled by Lone Electron Pair Activity.

Gomes Eduardo O EO Gouveia Amanda F AF Gracia Lourdes L Lobato Álvaro Á Recio J Manuel JM Andrés Juan J

The journal of physical chemistry letters 20221017 42

The chemical pressure approach offers a new paradigm for property control in functional materials. In this work, we disclose a correlation between the β → α pressure-induced phase transition in SnMoO4 and the substitution process of Mo6+ by W6+ in SnMo1-xWxO4 solid solutions (x = 0-1). Special attention is paid to discriminating the role of the lone pair Sn2+ cation from the structural distortive ef ...[more]

PMID: 36252084

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Project description:The monoclinic-to-hexagonal phase transition in mimetite Pb5(AsO4)3Cl was investigated by in situ temperature-dependent single crystal X-ray diffraction combined with ab initio molecular dynamics simulations. The crystal structure of mimetite Pb5(AsO4)3Cl, a phosphate with apatite structure-type has been investigated in situ at 123, 173, 273, 288, 353 and 393 K. A careful inspection of the diffraction pattern and subsequent structure refinements indicated that mimetite transforms from the monoclinic to the hexagonal polymorph with increasing temperature. At 123 K, a monoclinic superstructure, mimetite-2M, with cell parameters a = 20.4487 (9), b = 7.4362 (2), c = 20.4513 (9) Å, β = 119.953 (6)°, V = 2694.5 (2) Å3 and space group P21 was observed. From 173 to 353 K, the reflections of the supercell were evident only along one direction of the corresponding hexagonal apatite-cell and the structure transforms to the polymorph mimetite-M with space group P21/b and unit-cell parameters a = 10.2378 (3), b = 20.4573 (7), c = 7.4457 (2) Å, β = 120.039 (5)°, V = 1349.96 (9) Å3. Only at higher temperature, i.e. 393 K, does mimetite adopt the hexagonal space group P63/m characteristic of apatite structure-types. The role of the electron lone pairs of Pb atoms in the phase transition was investigated through the analysis of the electron localization function (ELF) calculated based on the DFT-geometry optimized structures of the three polymorphs. The changes in spatial distribution of the 6s2 electron density during the phase transitions were explored by means of the Wannier Function Centres (WFCs) derived from ab initio molecular dynamics trajectories. In the high-temperature hexagonal structure the 6s2 electrons are spherically symmetric relative to the position of Pb atoms. At low temperature the maximum of 6s2 electron density is displaced relative to the position of Pb atom contributing to the polar interaction in the monoclinic polymorphs.

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A Chemical-Pressure-Induced Phase Transition Controlled by Lone Electron Pair Activity.

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A Chemical-Pressure-Induced Phase Transition Controlled by Lone Electron Pair Activity.

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