First principles study of the electronic, elastic and vibrational properties of BiOI

Bandlike Transport and Charge-Carrier Dynamics in BiOI Films

“…Broad features at intermediate values (∼2.0 and ∼3.8 THz) could be associated with one or more optical phonon modes that are less IR active and appear to be very broad. We note that these experimentally determined peaks at 1.3, 2.0, and 7.0 THz exhibit respectable agreement with theoretically predicted IR-active modes occurring at 1.65, 2.88, and 8.88 THz . The first-principles simulation attributed the phonon modes at 1.65 and 2.88 THz to Bi–I vibrations, whereas the mode at 8.88 THz was suggested to originate from in-plane vibration of O atoms; however, no theoretical assignment of the peak we observe at 3.75 THz has been made to date.…”

“…We note that these experimentally determined peaks at 1.3, 2.0, and 7.0 THz exhibit respectable agreement with theoretically predicted IRactive modes occurring at 1.65, 2.88, and 8.88 THz. 53 The first-principles simulation attributed the phonon modes at 1.65 and 2.88 THz to Bi−I vibrations, whereas the mode at 8.88 THz was suggested to originate from in-plane vibration of O atoms; however, no theoretical assignment of the peak we observe at 3.75 THz has been made to date. Complementary Raman investigations have been reported for single crystals of BiOI revealing additional Raman-active phonon modes at 50 cm −1 (1.50 THz) and 86 cm −1 (2.58 THz).…”