Pressure-induced ferroelastic phase transition in SnO2 from density functional theory.
High-pressure ferroelastic transition of rutile- to CaCl2-type SnO2 is investigated within density functional theory and Landau free energy theory. The calculated Landau energy map around the ground state is successfully used to clarify the softening mechanism of B1g mode (order parameter Q) and the coupling mechanism between the soft B1g mode and the soft transverse acoustic (TA) mode (strain ɛ). It is found that the Sn-O-Sn bending induced soft B1g mode effectively slows the excess energy increase caused by bond stretching, while the coupling between the soft B1g mode and the soft TA mode further decreases the energy since the lattice distortion strain ɛ minimizes the SnO6 octahedral distortion. Q induced Landau Gibbs free energy is interpreted as the sum of the bond stretching energy, bending energy, and octahedral distortion energy, while that induced by ɛ is interpreted as the lattice distortion energy.
State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China.
Lei
L
Yang
School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, People's Republic of China.
Weiliu
W
Fan
Lehrstuhl für Theoretische Physik, Universität Paderborn, Paderborn 33095, Germany.
Yanlu
Y
Li
State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China.
Lei
L
Wei
State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China.
Xian
X
Zhao