fig1
![Microstructural evolution and ferroelectricity in HfO<sub>2 </sub>films](https://image.oaes.cc/acb286e2-3aef-4c4b-b87e-31f17f58d8a1/4637.fig.1.jpg)
Figure 1. Symmetry-reduction flowchart of low energy phases of HfO2, starting from the C-phase. The left branch shows stable non-polar phases and the right branch presents polar phases obtained from first-principles calculations. Dark yellow and red spheres represent hafnium and oxygen atoms, respectively, while green spheres indicate the center of symmetry of the centrosymmetric phases[38].