A Sodium Germanosilicide with Unusual Network Topology.

The germanosilicide NaGeSi (0.4 ≤ ≤ 1.1, 4.

Extensively Microtwinned Diamond with Nanolaminates of Lonsdaleite Formed by Flash Laser Heating of Glassy Carbon.

Diamond's unique properties on the nanoscale make it one of the most important materials for use in biosensors and quantum computing and for components that can withstand the harsh environments of space. We synthesize oriented, faceted diamond particles by flash laser heating of glassy carbon at 16 GPa and 2300 K. Detailed transmission electron microscopy shows them to consist of a mosaic of diamond nanocrystals frequently joined at twin boundaries forming microtwins.

Bulk Crystalline 4H-Silicon through a Metastable Allotropic Transition.

We report the synthesis of bulk, highly oriented, crystalline 4H hexagonal silicon (4H-Si), through a metastable phase transformation upon heating the single-crystalline Si_{24} allotrope. Remarkably, the resulting 4H-Si crystallites exhibit an orientation relationship with the Si_{24} crystals, indicating a structural relationship between the two phases. Optical absorption measurements reveal that 4H-Si exhibits an indirect band gap near 1.

Investigation of Room Temperature Formation of the Ultra-Hard Nanocarbons Diamond and Lonsdaleite.

Diamond is an attractive material due to its extreme hardness, high thermal conductivity, quantum optical, and biomedical applications. There is still much that is not understood about how diamonds form, particularly at room temperature and without catalysts. In this work, a new route for the formation of nanocrystalline diamond and the diamond-like phase lonsdaleite is presented.

Understanding the Unusual Response to High Pressure in KBeBOF.

Strong anisotropic compression with pressure on the remarkable non-linear optical material KBeBOF has been observed with the linear compression coefficient along the c axis found to be about 40 times larger than that along the a axis. An unusual non-monotonic pressure response was observed for the a lattice parameter. The derived bulk modulus of 31 ± 1 GPa indicates that KBeBOF is a very soft oxide material yet with stable structure up to 45 GPa.

Nanocrystalline hexagonal diamond formed from glassy carbon.

Carbon exhibits a large number of allotropes and its phase behaviour is still subject to significant uncertainty and intensive research. The hexagonal form of diamond, also known as lonsdaleite, was discovered in the Canyon Diablo meteorite where its formation was attributed to the extreme conditions experienced during the impact. However, it has recently been claimed that lonsdaleite does not exist as a well-defined material but is instead defective cubic diamond formed under high pressure and high temperature conditions.