Diversity of Molecular-Network Conformations in the Over-Stoichiometric Arsenoselenides Covering a Full Thioarsenides
Oleh Shpotyuk1,2,3, Malgorzata Hyla1, Zdenka Lukáčová Bujňáková4
1Institute of Physics, Jan Dlugosz University in Częstochowa, 13/15, al. Armii Krajowej, 42-200 Częstochowa, Poland.
Abstract:
Molecular network conformations in the over-stoichiometric arsenoselenides of canonical AsxSe100-x system (40 ≤ x ≤ 100) covering a full row of thioarsenide-type As4Sen entities (0 ≤ n ≤ 6) are analyzed with ab initio quantum-chemical modeling employing cluster-simulation code CINCA. Native (melt-quenching-derived) and nanostructurization-driven (activated by nanomilling) polymorphic and polyamorphic transitions initiated by decomposition of the thioarsenide-type As4Sen cage molecules and incorporation of their remnants into a newly polymerized arsenoselenide network are identified on the developed map of molecular network clustering in a binary As-Se system. Within this map, compositional counter lines corresponding to preferential molecular or network-forming tendencies in the examined arsenoselenides are determined, explaining that network-crystalline conformations prevail in the boundary compositions corresponding to n = 6 and n = 0, while molecular-crystalline ones dominate inside the rows corresponding to n = 4 and n = 3. A set of primary and secondary equilibrium lines is introduced in the developed clustering map to account for inter-phase equilibria between the most favorable (regular) and competitive (irregular) thioarsenide phases. Straightforward interpretation of decomposition reactions accompanying induced crystallization and amorphization (reamorphization) in the arsenoselenides is achieved, employing disproportionality analysis of thioarsenide-type molecular network conformations within the reconstructed clustering map. The preference of network clustering at the boundaries of the As4Sen row (at n = 6 and n = 0) disturbs inter-phase equilibria inside this row, leading to unexpected anomalies, such as absence of stable tetra-arsenic triselenide As4Se5 molecular-crystalline species; polyamorphism in mechanoactivated As4Sen alloys (2 ≤ n ≤ 6); breakdown in the glass-forming ability of melt-quenching-derived arsenoselenides in the vicinity of tetra-arsenic biselenide As4Se2 composition; plastically and normally crystalline polymorphism in tetra-arsenic triselenide As4Se3-based thioarsenides, and so on.
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