Phase transition and elastic and optical properties of Lu2SiO5

• The C2/c phase is found to be stable at ambient conditions.
• The phase transition from C2/c to P21/c phase is predicted to occur at 6.3 GPa.
• The reflectivity of LSO crystal is found to be 0.1.

Cerium-doped lutetium silicate (LSO:Ce) crystal is a well-known scintillator. However, there are two different structures reported for LSO crystal at ambient conditions in experiments. The structural, elastic, electronic and optical properties of the C2/c and P21/c phases of LSO crystal have been investigated using first-principles method. The C2/c phase is found to be stable at ambient conditions. The phase transition from C2/c phase to P21/c phase is predicted to occur at 6.3 GPa, together with a volume contraction of 3.7%. The bulk modulus of the C2/c phase is larger than the P21/c phase. The hybridization of O-2p and Si-3p is found in the upper valence band of LSO crystal. The C2/c and P21/c phases are predicted to be insulators with calculated gaps of 4.67 and 4.80 eV, respectively. The refractive index of LSO crystal is found to be about 1.9 for both phases.