Nonreversible Transition from the Hexagonal to Wurtzite Phase of Boron Nitride under High Pressure: Optical Properties of the Wurtzite Phase

This work has been supported by the Spanish MINECO/FEDER under contracts no. MAT2015-71035-R and no.MAT2016-75586-C4-1-P. T.T. acknowledges support from the Elemental Strategy Initiative conducted by the MEXT, Japan and JSPS KAKENHI grant number JP15K21722. B.G. acknowledges support from the Government of the Russian Federation, contract #14.W03.31.0011 at Ioffe Institute.