Defect chemistry of lone-pair semiconductors

TLDR

Unusual low‑energy bonding configurations arise in lone‑pair semiconductors, with valence‑alternation pairs (V.A.P.) as a key concept. The study examines the nature of V.A.P.s in pnictide semiconductors and explores whether these centers can form bound pairs. The authors detail the interconversion mechanism between positive and negative V.A.P. centers.

Abstract

Abstract A chemical-bond approach reveals the possibility of several unusual bonding configurations that have relatively low energy in materials with lone-pair valence electrons. Valence-alternation pairs (V.A.P.) are the lowest energy charged defects. The interconversion between positive and negative centres is described in detail. The nature of V.A.P.s in pnictides (group V elements) is discussed. The possibility that valence-alternation centres can form intimate or bound pairs is explored. It is pointed out that certain unusual bonding configurations (configuration distortions) arise even in an ideal lone-pair material. It is stressed that the unusual bonding configurations discussed are a result of the special bonding in lone-pair materials and are, therefore, expected to arise in crystals as well as amorphous materials.