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Understanding the Structure and Properties of Sesqui‐Chalcogenides (i.e., V 2 VI 3 or Pn 2 Ch 3 (Pn = Pnictogen, Ch = Chalcogen) Compounds) from a Bonding Perspective
Author(s) -
Cheng Yudong,
CojocaruMirédin Oana,
Keutgen Jens,
Yu Yuan,
Küpers Michael,
Schumacher Mathias,
Golub Pavlo,
Raty JeanYves,
Dronskowski Richard,
Wuttig Matthias
Publication year - 2019
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201904316
Subject(s) - chalcogen , pnictogen , materials science , density functional theory , van der waals force , ionic bonding , natural bond orbital , chemical bond , chemical physics , dielectric , lone pair , computational chemistry , crystallography , condensed matter physics , nanotechnology , chemistry , molecule , ion , physics , optoelectronics , superconductivity , organic chemistry
A number of sesqui‐chalcogenides show remarkable properties, which make them attractive for applications as thermoelectrics, topological insulators, and phase‐change materials. To see if these properties can be related to a special bonding mechanism, seven sesqui‐chalcogenides (Bi 2 Te 3 , Bi 2 Se 3 , Bi 2 S 3 , Sb 2 Te 3 , Sb 2 Se 3 , Sb 2 S 3 , and β‐As 2 Te 3 ) and GaSe are investigated. Atom probe tomography studies reveal that four of the seven sesqui‐chalcogenides (Bi 2 Te 3 , Bi 2 Se 3 , Sb 2 Te 3 , and β‐As 2 Te 3 ) show an unconventional bond‐breaking mechanism. The same four compounds evidence a remarkable property portfolio in density functional theory calculations including large Born effective charges, high optical dielectric constants, low Debye temperatures and an almost metal‐like electrical conductivity. These results are indicative for unconventional bonding leading to physical properties distinctively different from those caused by covalent, metallic, or ionic bonding. The experiments reveal that this bonding mechanism prevails in four sesqui‐chalcogenides, characterized by rather short interlayer distances at the van der Waals like gaps, suggestive of significant interlayer coupling. These conclusions are further supported by a subsequent quantum‐chemistry‐based bonding analysis employing charge partitioning, which reveals that the four sesqui‐chalcogenides with unconventional properties are characterized by modest levels of charge transfer and sharing of about one electron between adjacent atoms. Finally, the 3D maps for different properties reveal discernible property trends and enable material design.