CuBiP
2Se
6, AgBiP
2Se
6, and AgBiP
2S
6 were prepared from the corresponding elements. CuBiP
2Se
6 and AgBiP
2Se
6crystallize in the space group
R![](/images/entities/thremacr.gif)
with
a = 6.5532(16) Å and
c = 39.762(13) Å for CuBiP
2Se
6 and
a =6.6524(13) Å and
c = 39.615(15) Å for AgBiP
2Se
6. AgBiP
2S
6 crystallizes in the triclinic space group
P![](/images/entities/onemacr.gif)
with
a =6.3833(13) Å,
b = 7.1439(14) Å,
c = 9.5366(19) Å,
![](/images/gifchars/alpha.gif)
= 91.89(3)
![](/images/entities/deg.gif)
,
![](/images/gifchars/beta2.gif)
= 91.45(3)
![](/images/entities/deg.gif)
,
![](/images/gifchars/gamma.gif)
= 94.05(3)
![](/images/entities/deg.gif)
. CuBiP
2Se
6was found to exhibit a temperature-dependent antiferroelectric ordering of the Cu
+ and Bi
3+ ions in the lattice. Anintermediate and a fully ordered structure were refined at 173 and 97 K, respectively. Electronic band and totalenergy calculations at the DFT level clearly suggest that the antiferroelectric model is energetically favored overthe paraelectric and hypothetical ferrielectric models. This phase transition can be classified as a second-orderJahn-Teller distortion. The antiferroelectric state of CuBiP
2Se
6 is an indirect gap semiconductor. The compoundswere characterized with differential thermal analysis and solid-state UV/vis diffuse reflectance spectroscopy.Generalized implications regarding the expected ferroelectric behavior of compounds in the CuMP
2Se
6 system (M= trivalent metal) are discussed.