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Background theory. In the harmonic approximation, the potential energy surface (PES) is expanded about an equilibrium point to second order, to obtain the Hamiltonian: $$ \hat{H}=\sum_{p,\alpha}-\frac{1}{2m_{\alpha}}\nabla_{p\alpha}^2+\frac{1}{2}\sum_{p,\alpha,i}\sum_{p^{\prime},\alpha^{\prime},i^{\prime}}D_{i\alpha;i^{\prime}\alpha^{\prime}}(\mathbf{R}_p,\...


12

The answer of @ProfM is already very complete, but I wanted to tackle your question from a more practical point of view. The presence of imaginary frequencies indicate that there are atomic positions which are more energetically favorable at the ground state. So, the concept of "following" a mode means condensing it onto the reference structure, ...


10

If you are looking for theoretical prediction of candidate perovskite solar cell materials; I have come across several papers that couple high-throughput density functional theory calculations along with machine learning for new material prediction. I haven't seen any solar cell compound discovery theoretical work that eventually validated their predictions ...


7

While I can't speak to the specific interest of solar cells, Perovskite is the primary ore source for Titanium. Owing to the fact that alloys of Titanium played a critical role in modernization of weapons technologies that occurred during the cold war period, there was a LOT of research money into titanium projects during the 1970s to early 1990s. For ...


5

To add to the previous answer: the new lead-free halide double perovskite $\ce{Cs_2InAgCl_6}$ was discovered by first-principles and then synthesized: G. Volonakis et al. $\ce{Cs_2InAgCl_6}$: A New Lead-Free Halide Double Perovskite with Direct Band Gap, J. Phys. Chem. Lett. 8, 772 (2017) https://pubs.acs.org/doi/10.1021/acs.jpclett.6b02682 I'm sure there ...


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