Fig. 2: Relevant results of DFT theoretical calculation.
From: Achieving a high dielectric tunability in strain-engineered tetragonal K0.5Na0.5NbO3 films
a Schematic diagram of ideal paraelectric KNN structure. The K/Na atom in the structure are ordered along [001] direction. The atoms in yellow, purple, green, and red are K, Na, Nb, and O, respectively. The unit cell in black frame and the supercell in red frame contains 10 and 20 atoms, respectively, and will be used in our calculation for different KNN phases, i.e., P4mm (10 atoms) and C2mm (20 atoms). b Free energies of the P4mm and C2mm phases as functions of the misfit strain.
