Due to the weak interlayer interactions,the binary Ⅲ-Ⅵ chalcogenides Ga Se can exist in several distinct polymorphs.Among them,the so-called β-and ε-phases simultaneously exhibit favorable total energies and moder...Due to the weak interlayer interactions,the binary Ⅲ-Ⅵ chalcogenides Ga Se can exist in several distinct polymorphs.Among them,the so-called β-and ε-phases simultaneously exhibit favorable total energies and moderate band gaps,which offer a good platform to explore their thermoelectric properties.Here,we demonstrate by first-principles calculations that the two systems have very similar band structures and phonon dispersions,despite different stacking sequences between adjacent layers.Interestingly,the lattice thermal conductivity of ε-GaSe is obviously lower than that of β-GaSe,which is inherently tied to stronger lattice anharmonicity caused by bonding heterogeneity.Besides,both systems exhibit higher p-type power factors due to doubly degenerate bands with weaker dispersions around the valence band maximum.As a consequence,a significantly enhanced p-type figure-of-merit of 2.1 can be realized at 700 K along the out-of-plane direction of theε-phase.展开更多
Symmetry typically characterizes the impact of a liquid droplet on a solid surface,where uniform spreading is followed by radial retraction.Breaking this symmetry tra-ditionally relies on engineering surface propertie...Symmetry typically characterizes the impact of a liquid droplet on a solid surface,where uniform spreading is followed by radial retraction.Breaking this symmetry tra-ditionally relies on engineering surface properties.Here,we introduce an alternative approach to achieve asymmetric droplet impact by incorporating a pair of bubbles into the liquid droplet,resulting in the coexistence of spreading and retraction.The asym-metric dynamics originate from the anisotropic capillary effects that can be adjusted by varying the volume fraction of bubbles and the impact velocity.The early onset of retraction enhances upward liquid momentum,facilitating prompt droplet takeoff and significantly reducing both the contact area(up to 50%)and contact time(up to 60%).Thisreductionalsodiminishesheat exchangebetweenthedroplet andthesurface.Our findings pave the way for applications that capitalize on reduced contact times through droplet engineering,eliminating the need for surface modifications.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.62074114 and 12474019)。
文摘Due to the weak interlayer interactions,the binary Ⅲ-Ⅵ chalcogenides Ga Se can exist in several distinct polymorphs.Among them,the so-called β-and ε-phases simultaneously exhibit favorable total energies and moderate band gaps,which offer a good platform to explore their thermoelectric properties.Here,we demonstrate by first-principles calculations that the two systems have very similar band structures and phonon dispersions,despite different stacking sequences between adjacent layers.Interestingly,the lattice thermal conductivity of ε-GaSe is obviously lower than that of β-GaSe,which is inherently tied to stronger lattice anharmonicity caused by bonding heterogeneity.Besides,both systems exhibit higher p-type power factors due to doubly degenerate bands with weaker dispersions around the valence band maximum.As a consequence,a significantly enhanced p-type figure-of-merit of 2.1 can be realized at 700 K along the out-of-plane direction of theε-phase.
基金Research Grants Council of Hong Kong,Grant/Award Number:21213621National Natural Science Foundation of China,Grant/Award Number:52303046City University of Hong Kong,Grant/Award Number:7006097。
文摘Symmetry typically characterizes the impact of a liquid droplet on a solid surface,where uniform spreading is followed by radial retraction.Breaking this symmetry tra-ditionally relies on engineering surface properties.Here,we introduce an alternative approach to achieve asymmetric droplet impact by incorporating a pair of bubbles into the liquid droplet,resulting in the coexistence of spreading and retraction.The asym-metric dynamics originate from the anisotropic capillary effects that can be adjusted by varying the volume fraction of bubbles and the impact velocity.The early onset of retraction enhances upward liquid momentum,facilitating prompt droplet takeoff and significantly reducing both the contact area(up to 50%)and contact time(up to 60%).Thisreductionalsodiminishesheat exchangebetweenthedroplet andthesurface.Our findings pave the way for applications that capitalize on reduced contact times through droplet engineering,eliminating the need for surface modifications.
