Speaker
Description
According to Benedek et. al [1], the CsNdNb$_{2}$O$_{7}$ system undergoes two phase transitions, one at 625 K and another at 800 K. Our objective is to investigate those three distinct phases: $P2_{1}am$ (# 26), $C2/m$ (# 12) and $P4/mmm$ (# 123) [1].
There is no existing literature discussing the magnetic state of CsNdNb$_{2}$O$_{7}$. Nevertheless, due to the presence of three unpaired electrons in the $4f$ orbital of the Nd atoms, this material is expected to exhibit magnetic properties.
Benedek and her research group simulated the system by freezing the $\textit{4f}^3$ electrons in the core [2], employing a non-polarized simulation.
We initiated our study with an investigation into the optimal approach for simulating the CsNdNb$_{2}$O$_{7}$ system. To accomplish this, we conducted a thorough analysis by comparing spin-polarized with Hubbard correction and non-polarized models. We demonstrated the necessity of a Hubbard correction for the spin-polarized model, wherein we obtained an $\textit{ab-initio}$ estimate of the Hubbard parameter as 4.15 eV for the $P4/mmm$ (aristotype) phase. This value is in our spin-polarized simulations, although further investigation is being held to obtain an accurate estimate for the ground state. Additionally, we expanded our investigation to include the CsLaNb$_{2}$O$_{7}$ system, which exhibits non-magnetic characteristics, thereby offering a valuable point of comparison in our study.
Thus, through the analysis of the Density of States (DOS) and the Electrical Field Gradients (EFG) of the different models, we will determine the optimal approach for simulating CsNdNb$_{2}$O$_{7}$ and potentially other members of the Dion-Jacobson family of naturally layered perovskites.
$\textbf{References}$
$\lbrack$1$\rbrack$ - Zhu T., Gibbs A.S., Benedek N.A. and Hayward M.A., Chemistry of Materials 32, 10, 4340–4346 (2020).
$\lbrack$2$\rbrack$ - Benedek N.A., Inorganic Chemistry 53, 7, 3769–3777 (2014).
