Energetic stability, structural transition, and thermodynamic properties of ZnSnO[sub 3]

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98679/1/ApplPhysLett_98_091914.pd

Pressure-stabilized divalent ozonide CaO3 and its impact on Earth's oxygen cycles.

High pressure can drastically alter chemical bonding and produce exotic compounds that defy conventional wisdom. Especially significant are compounds pertaining to oxygen cycles inside Earth, which hold key to understanding major geological events that impact the environment essential to life on Earth. Here we report the discovery of pressure-stabilized divalent ozonide CaO3 crystal that exhibits intriguing bonding and oxidation states with profound geological implications. Our computational study identifies a crystalline phase of CaO3 by reaction of CaO and O2 at high pressure and high temperature conditions; ensuing experiments synthesize this rare compound under compression in a diamond anvil cell with laser heating. High-pressure x-ray diffraction data show that CaO3 crystal forms at 35 GPa and persists down to 20 GPa on decompression. Analysis of charge states reveals a formal oxidation state of -2 for ozone anions in CaO3. These findings unravel the ozonide chemistry at high pressure and offer insights for elucidating prominent seismic anomalies and oxygen cycles in Earth's interior. We further predict multiple reactions producing CaO3 by geologically abundant mineral precursors at various depths in Earth's mantle

Diamane: design, synthesis, properties, and challenges

Diamane, the two-dimensional counterpart of diamond, is achieved from bi-layer graphene (BLG) or few-layer graphene (FLG) through surface chemical adsorption or high-pressure technology. Diamane with interlayer sp3 bonding is found to have excellent heat transfer, ultra-low friction, high natural frequency, and tunable band gap, which shows the potential technological and industrial applications in nano-photonics, ultrasensitive resonator-based sensors, and improved wear resistance. In this review, we summarize the structure character, synthesis strategies, and physical properties of different diamanes, including hydrogenated diamane (HD), fluorinated diamane (FD), and pristine diamane (PD). In addition, we discuss the effect of functional groups, element doping, and stacking order on the physical properties of diamane. Finally, the remaining challenges and future opportunities for the further development of diamane are addressed

Room-Temperature Synthesis of Tubular Hexagonal Boron Nitride under Pressure

Hexagonal boron nitride (h-BN) exhibits interesting optical and mechanical properties, including chemical and thermal stability. Extensive techniques have been applied for the realization of h-BN at high temperatures. Here, we propose a room-temperature preparation of h-BN at high pressure through the compression of ammonium azide and boron powder. The structure and morphology of the obtained h-BN are found to possess tubular-like features, and the selected-area electron diffraction and electron energy-loss spectroscopy support the formation of h-BN. Remarkably, h-BN grows gradually from the surface of boron particles to form a core–shell structure. This tubular morphology of h-BN with a size of 70 nanometers in length and 27 nanometers in width differs from the conventional lamellar h-BN generated with temperature assistance. Our results demonstrate a method for the room-temperature synthesis of tubular h-BN, which shows great promise for the preparation of other nitrides at high pressure and room temperature