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 SnMo1–x W x O4 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.

Structural Phase Transition in 0D (3,5-DMP)2Bi1–xSbxCl5 Metal Halides: Expression of the Lone Pair Effect and Polyhedral Distortion

“…Further, the dimeric [Sb 2 Cl 10 ] 4– units are more distorted as compared to [Bi 2 Cl 10 ] 4– units. The relatively longer bridged Sb–Cl bond and more distorted [Sb 2 Cl 10 ] 4– units are attributed to the greater stereochemical activity of the 5s 2 lone pair of Sb 3+ ion than the 6s 2 lone pair of Bi 3+ . ,− The repulsion caused by the stereoactive 5s 2 lone pair electrons of Sb 3+ is significant and more as compared to the 6s 2 lone pair of Bi and hence the [Sb 2 Cl 10 ] 4– units undergo more distortion. ,,, The extent of octahedral distortion for all the compounds can be quantified based on their variation of M–Cl bond lengths ( λ oct = quadratic elongation) and ∠Cl–M–Cl bond angles ( σ 2 = bond angle variance). , λ oct = 1 6 ∑ n = 1 6 false[ false( d n − d 0 false) / d 0 false] 2 σ 2 = 1 11 ∑ n = 1 12 false( θ n − 90 ° false) 2 …”

Electron-deficient multicenter bonding in pnictogens and chalcogens: mechanism of formation

“…Therefore, other ways of increasing electronic density could also lead to a decrease in the LEP stereoactivity and the formation of EDMBs. Two examples are chemical pressure 167 and reduction, i.e. providing electrons to the system.…”

Metavalent multicenter bonding in pnictogens and chalcogens: nature and mechanism of formation

“…Therefore, other ways of increasing electronic density could also lead to a decrease in the LEP stereoactivity and the formation of EDMBs. Two examples are chemical pressure [207] and reduction, i.e. providing electrons to the system [51].…”