Cubic Stuffed-Diamond Semiconductors LiCu₃TiQ₄ (Q = S, Se, and Te)

Abstract

Lithium chalcogenides have been understudied, owing to the difficulty in managing the chemical reactivity of lithium. These materials are of interest as potential ion conductors and thermal neutron detectors. In this study, we describe three new cubic lithium copper chalcotitanates that crystallize in the P4̅ 3m space group. LiCu 3 TiS 4 , a = 5.5064(6) Å, and LiCu 3 TiSe 4 , a = 5.7122(7) Å, represent two members of a new stuffed diamond-type crystal structure, while LiCu 3 TiTe 4 , a = 5.9830(7) Å crystallized into a similar structure exhibiting lithium and copper mixed occupancy. These structures can be understood as hybrids of the zinc-blende and sulvanite structure types. In situ powder X-ray diffraction was utilized to construct a "panoramic" reaction map for the preparation of LiCu 3 TiTe 4 , facilitating the design of a rational synthesis and uncovering three new transient phases. LiCu 3 TiS 4 and LiCu 3 TiSe 4 are thermally stable up to 1000 °C under vacuum, while LiCu 3 TiTe 4 partially decomposes when slowly cooled to 400 °C. Density functional theory calculations suggest that these compounds are indirect band gap semiconductors. The measured work functions are 4.77(5), 4.56(5), and 4.69(5) eV, and the measured band gaps are 2.23(5), 1.86(5), and 1.34(5) eV for the S, Se, and Te analogues, respectively.

Disorder-Mediated Structural Transformation in the Cu4TiSe4–xSx (0 ≤ x ≤ 4) System and Its Effects on the Thermal Transport Property

“…Conspicuously, this newly appeared Cu–Ti distance (∼2.3 Å) is significantly shorter than the reported one in the Cu–Ti-based compounds (Table S7). − To avoid these short Cu–Ti contacts, these Ti atoms need to shift by (1/2 1/2 0) along the shaded ab -plane (as shown in Figure ). As a consequence, the unit cell changes from tetragonal (hypothetical) to cubic (experimental).…”

Cu4TiTe4: Synthesis, Crystal Structure, and Chemical Bonding

“…A detailed in situ powder X-ray diffraction study might be a suitable tool for this. A similar kind of problem has been recently solved using this technique adopted by Quintero and Kanatzidis et al for the LiCu 3 TiTe 4 system …”

“…A similar kind of problem has been recently solved using this technique adopted by Quintero and Kanatzidis et al for the LiCu 3 TiTe 4 system. 42 3.2. Structure Solution, Refinement, and Phase Analysis.…”

Mechanistically Guided Materials Chemistry: Synthesis of Ternary Nitrides, CaZrN2 and CaHfN2

“…Within this current paradigm, in situ X-ray diffraction (XRD) is a powerful technique for materials discovery. 16,18−22 Sometimes called "panoramic synthesis," [18][19][20]22 in situ X-ray diffraction allows for observation of solid-state reactivity as it happens. Shortlived intermediate species and subtle crystallographic changes can be detected that would otherwise be missed by ex situ experiments, accelerating materials discovery.…”

“…Predictive synthesis remains an important goal for materials chemists. − While many joint computational-experimental synthesis efforts have been reported in literature, − trial-and-error approaches remain the dominant paradigm. Within this current paradigm, in situ X-ray diffraction (XRD) is a powerful technique for materials discovery. ,− Sometimes called “panoramic synthesis,” − , in situ X-ray diffraction allows for observation of solid-state reactivity as it happens. Short-lived intermediate species and subtle crystallographic changes can be detected that would otherwise be missed by ex situ experiments, accelerating materials discovery.…”