Sharad Babu Pillai

First principles calculation of two dimensional antimony and antimony arsenide

This work focuses on the strain dependence of the electronic properties of two dimensional antimony (Sb) material and its alloy with As (SbAs) using density functional theory based first principles calculations. Both systems show indirect bandgap semiconducting character which can be transformed into a direct bandgap material with the application of relatively small strain.

Strain effect on electronic and lattice dynamical behaviour of two dimensional Bi, BiAs and BiSb

The present study investigates the electronic band structure and lattice dynamical stability of 2D monolayer sheet of Bi, BiAs and BiSb using density functional theory based on first principles calculation. All these systems are semiconductor with direct bandgap. Under tensile strain the bandgap reduces and no bandgap closing is observed upto +5% strain whereas a direct-indirect-metal transition is observed for compressive strain in all these systems. The lattice dynamical stability of these materials has been studied under strain.The present study investigates the electronic band structure and lattice dynamical stability of 2D monolayer sheet of Bi, BiAs and BiSb using density functional theory based on first principles calculation. All these systems are semiconductor with direct bandgap. Under tensile strain the bandgap reduces and no bandgap closing is observed upto +5% strain whereas a direct-indirect-metal transition is observed for compressive strain in all these systems. The lattice dynamical stability of these materials has been studied under strain.

Strain induced changes in phonon band structure of antimony monolayer using density functional theory calculations

The present paper reports the study of phonon properties of a two dimensional antimony nanosheet under the biaxial strain using first principles calculation based on density functional theory. Our calculations shows that the strain turns the quadratic dependence of wave vector on frequency to the linear dependency which can be linked with the removal of rippling in nanosheets.

First principles study of hydrogen bond symmetrization in δ-AlOOH

The high pressure behaviour of the hydrous mineral δ-AlOOH has been investigated by many experimental and theoretical studies, but the discrepancy in predicting the value of hydrogen symmetrization pressure was not resolved. Here, we investigated the high pressure behaviour of δ-AlOOH using first principles calculations and found that with proper optimization using pressure routine control, local density approximation (LDA) predicts the hydrogen symmetrization pressure as 15 GPa which is in good agreement with the experimentally predicted value which resolves the existing discrepancy and hence proving the validity of LDA in predicting the hydrogen symmetrization pressure. We further studied the compressibility behaviour of δ-AlOOH at low pressures and confirmed the P21nm to Pnnm transition of δ-AlOOH shown by the experimental work [Kuribayashi et al., Phys. Chem. Miner. 41, 303–312 (2014)]. We have also analysed the dependence of elastic constants, elastic moduli, sound velocities, and Raman spectrum of δ-AlOOH with pressure and found that a subtle change in the position of the hydrogen atom at hydrogen symmetrization pressure results into drastic changes in elastic and vibrational properties. Further, this study has been used to discuss the seismic anomalies observed in the upper mantle beneath the Deccan Volcanic Province in India and the Java subduction zone in the eastern flank of the Indian Ocean.The high pressure behaviour of the hydrous mineral δ-AlOOH has been investigated by many experimental and theoretical studies, but the discrepancy in predicting the value of hydrogen symmetrization pressure was not resolved. Here, we investigated the high pressure behaviour of δ-AlOOH using first principles calculations and found that with proper optimization using pressure routine control, local density approximation (LDA) predicts the hydrogen symmetrization pressure as 15 GPa which is in good agreement with the experimentally predicted value which resolves the existing discrepancy and hence proving the validity of LDA in predicting the hydrogen symmetrization pressure. We further studied the compressibility behaviour of δ-AlOOH at low pressures and confirmed the P21nm to Pnnm transition of δ-AlOOH shown by the experimental work [Kuribayashi et al., Phys. Chem. Miner. 41, 303–312 (2014)]. We have also analysed the dependence of elastic constants, elastic moduli, sound velocities, and Raman spectrum of δ...