GaN-ZnO alloys are more promising semiconductors than their counterparts for optoelectronic applications due to the abrupt red shift in the visible-light range. Unfortunately, the strong internal electrostatic field (IEF) seriously...
Enhanced anharmonicity is required to achieve many interesting
phenomena in thermoelectricity, superconductivity, ferroelectricity,
etc. Here, we propose a novel mechanism for enhancing anharmonicity
by forming the low-symmetry off-center ground state, such as the s(II)
phase, in two-dimensional A
IB
2X chalcogenides (A
IB
= Cu, Ag and Au;
X = S, Se, and Te). In this system, the in-plane rotational phonon
mode introduces a much stronger anharmonicity in the distorted s(II)
phase than in the nondistorted s(I) phase. We show that the stabilities
of the s(I) and s(II) phases arise from the ionicity and the ionic
size; for example, the low ionicity and the small ionic size favor
the s(II) phase. We further demonstrate that the anharmonicity can
be tuned by controlling the strain-induced s(II)-to-s(I) phase transition,
which explains the anomalous lattice thermal conductivity. Our work
relates anharmonicity to symmetry-breaking structural distortion and
widens the ways to design excellent thermoelectric materials.
when exploring the parameters for the coal and waste rock, eight characteristic parameters were selected as the whole characters of an image according to their significant differences in gray scale and texture features. On the basis, the error back-propagation algorithm of neural network is applied for the nonlinear identification of samples. The identification network was trained successfully through learning samples. Then, the validity of eight characteristic parameters was verified through the tests of experimental images. Meanwhile, the goal of intelligent identification of coal and waste rock is achieved successfully.
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