Effects of pressure on the structure and lattice dynamics of α-glycine: a combined experimental and theoretical study

Abstract

α-Glycine is studied up to 50 GPa using synchrotron angle-dispersive X-ray powder diffraction (XRD), Raman spectroscopy, and quantum chemistry calculations performed at multiples levels of theory. Results from both XRD and Raman experiments reveal an extended pressure stability of the α phase up to 50 GPa and the room temperature (RT) equation of state (EOS) was determined up to this pressure. This extended stability is corroborated by density functional theory (DFT) based calculations using the USPEX evolutionary structural search algorithm. Two calculated EOSs, as determined by DFT at T = 0 K and semiempirical density functional tight-binding (DFTB) at RT, and the calculated Raman modes frequencies show a good agreement with the corresponding experimental results. Our work provides a definitive phase diagram and EOS for α-glycine up to 50 GPa, which informs prebiotic synthesis scenarios that can involve pressures well in excess of 10 GPa.