Compressibility Studies of Copper Selenides Obtained by Cation Exchange Reaction Revealing the New CsCl Phase

In this study, we conducted a high-pressure
investigation of Cu2–xSe nanostructures
with pyramid-
and plate-like morphologies, created through cation exchange from
zinc-blende CdSe nanocrystals and wurtzite CdSe nanoplatelets respectively.
Using a diamond anvil cell setup at the APS synchrotron, we observed
the phase transitions in the Cu2–xSe nanostructures up to 40 GPa, identifying a novel CsCl-type lattice
with Pm3̅m symmetry above
4 GPa. This CsCl-type structure, previously unreported in copper selenides,
was partially retained after decompression. Our results indicate that
the initial crystalline structure of CdSe does not affect the stability
of Cu2–xSe nanostructures formed
via cation exchange. Both morphologies of Cu2–xSe sintered under compression, potentially contributing
to the stabilization of the high-pressure phase through interfacial
defects. These findings are significant for discovering new phases
with potential applications in future technologies.