Molecular Network <i>Polyamorphism</i> in Mechanically Activated Arsenic Selenides Under Deviation from As<sub>2</sub>Se<sub>3</sub> Stoichiometry
Polyamorphic transitions driven by high-energy mechanical milling (nanomilling) are studied in thioarsenide As<sub>4</sub>Se<sub>n</sub>-type glassy alloys obtained by melt quenching deviated from arsenic triselenide As<sub>2</sub>Se<sub>3</sub> stoich...
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| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-01-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/3/642 |
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| Summary: | Polyamorphic transitions driven by high-energy mechanical milling (nanomilling) are studied in thioarsenide As<sub>4</sub>Se<sub>n</sub>-type glassy alloys obtained by melt quenching deviated from arsenic triselenide As<sub>2</sub>Se<sub>3</sub> stoichiometry towards tetraarsenic pentaselenide (g-As<sub>4</sub>Se<sub>5</sub>) and tetraarsenic tetraselenide (g-As<sub>4</sub>Se<sub>4</sub>). This employs a multiexperimental approach based on powder X-ray diffraction (XRD) analysis complemented by thermophysical heat transfer, micro-Raman scattering (micro-RS) spectroscopy, and revised positron annihilation lifetime (PAL) analysis. Microstructure scenarios of these nanomilling-driven transformations in arsenoselenides are identified by quantum-chemical modeling using the authorized modeling code CINCA (the Cation Interlinked Network Cluster Approach). A straightforward interpretation of a medium-range structure response of a nanomilling-driven polyamorphism in the arsenoselenides is developed within the modified microcrystalline model. Within this model, the diffuse peak-halos arrangement in the XRD patterning is treated as a superposition of the Bragg-diffraction contribution from inter-planar correlations supplemented by the Ehrenfest-diffraction contribution from inter-atomic (inter-molecular) correlations related to derivatives of network As<sub>2</sub>Se<sub>3</sub>-type and molecular As<sub>4</sub>Se<sub>4</sub>-type conformations. Changes in the medium-range structure of examined glassy arsenoselenides subjected to nanomilling occur as an interplay between disrupted intermediate-range ordering and enhanced extended-range ordering. The domination of network-forming conformations in arsenoselenides deviated from As<sub>2</sub>Se<sub>3</sub> stoichiometry (such as g-As<sub>4</sub>Se<sub>5</sub>) results in rather slight changes in their calorimetric heat-transfer and micro-RS responses. At the atomic-deficient level probed by PAL spectroscopy, these changes are accompanied by reduced positron trapping rate of agglomerated multiatomic vacancies and vacancy-type clusters in an amorphous As-Se network. Under an increase in As content beyond the g-As<sub>4</sub>Se<sub>5</sub> composition approaching g-As<sub>4</sub>Se<sub>4</sub>, nanomilling-driven polyamorphic transitions, which can be classified as reamorphization (amorphous I-to-amorphous II) phase transitions, are essentially enhanced due to the higher molecularity of these glassy alloys enriched in thioarsenide-type As<sub>4</sub>Se<sub>4</sub> cage-like molecular entities and their low-order network-forming derivatives. |
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| ISSN: | 1420-3049 |