Understanding the unusual response to high pressure in KBe2BO3F2

Strong anisotropic compression with pressure on the remarkable non-linear optical material KBe2BO3F2 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 KBe2BO3F2 is a very soft oxide material yet with stable structure up to 45 GPa. A combination of high-pressure synchrotron powder X-ray diffraction, high-pressure Raman spectroscopy, and Density Functional Theory calculations points to the mechanism for the unusual pressure response being due to the competition between the K-F bond length and K-F-K bond angle and the coupling between the stretching and twisting vibration modes. This article is licensed under a Creative Commons Attribution 4.0 International License.
Nonlinear optics, Solids, Liquids, Anisotropy, Pressure range mega pa 10-100, X-ray diffraction, Lattice parameters, Raman spectroscopy, Monocrystals
Yu, D. H., Avdeev, M., Sun, D. H., Huston, L. Q., Shiell, T. B., Sun, Q. B., Lu, T., Gu, Q., Liu, H., Bradby, J. E., Yie, N., Liu, Y., Wang J. Y., & McIntyre, G. J. (2017). Understanding the unusual response to high pressure in KBe2BO3F2. Scientific Reports, 7, 4027. doi:10.1038/s41598-017-04323-2