High-Pressure Synthesized Materials: a Chest of Treasure and Hints
  The present review covers the production of new materials under high pressures. A primary limitation on the use of pressures higher than 1 GPa is a small volume and mass of a produced material. Therefore, despite an extremely wide range of new high-pressure synthesized substances with unique properties, synthesis on an commercial scale is applied up to now only to obtain superhard materials, this real treasure of today's industry. At the same time, high-pressure experiments often give material scientists a hint at what new intriguing substances can exist in principle. This is true for new superhard, semiconducting, magnetic, superconducting and optical materials already synthesized under pressure, and as well as for a large number of hypothetic new polymers from low-Z elements. Many of new materials, including the above polymers, may exist in the metastable form at normal pressure at sufficiently high temperatures. 
V.V. Brazhkin