posted on 2022-04-13, 12:04authored byBen Huang, Guodong Li, Chenyang Xiao, Bo Duan, Wenjuan Li, Pengcheng Zhai, William A. Goddard
For
practical applications of copper selenide (Cu2Se)
thermoelectric (TE) materials with liquid-like behavior, it is essential
to determine the structure–property relations as a function
of temperature. Here, we investigate β-Cu2Se structure
evolution during uniaxial compression over the temperature range of
400–1000 K using molecular dynamics simulations. We find that
at temperatures above 800 K, Cu2Se exhibits poor stability
with breaking order that is described as a liquid-like or hybrid structure
comprising a rigid Se sublattice and mobile Cu ions. A uniaxial load
causes accumulated structural heterogeneity that is alleviated by
diffusion-induced accommodation of local deformations. With increasing
strain, the deformation mode changes into a combination of compression
and shear, accompanied by restructuring in terms of twinning. Interestingly,
in addition to a plastic behavior rarely found in inorganic semiconductors,
we find that higher temperature promotes deformation twinning in liquid-like
Cu2Se, showing the role of thermal instability, including
Cu diffusion, in structural adaptation and mechanical modulation.
These findings reveal the micromechanism of hybrid structural evolution
as well as performance tuning through twinning, which provides a theoretical
guide toward advanced Cu2Se TE materials design.