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The synthesis of high-purity bulk nanostructured cubic boron nitride (cBN) at 20 GPa and 1770 K by direct phase transformation of graphite-like BN with an "ideal random layer" structure is reported. The two-times increase of hardness of nano-cBN (H(V) = 85 GPa) with respect to conventional polycrystalline cBN (H(V) ∼ 45 GPa) is evidently a result of nanosize effects.

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We present a neutron diffraction study of liquid water to 6.5 GPa and 670 K. From the measured structure factors we determine radial and angular distributions. It is shown that with increasing density water approaches a local structure common to a simple liquid while distorting only a little the tetrahedral first-neighbor coordination imposed by hydrogen bonds that remain intact.

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International audienceWe report accurate measurements of the equation of stat