Compounds based on Group 14 elements: building blocks for advanced insulator dielectrics design

Abstract

Being in the group with the most diverse set of properties among all in the periodic table, the Group 14 elements (C, Si, Ge, Sn, and Pb) are particularly interesting candidates for structure-property investigation. Motivated by the need to create new insulators for energy storage and electronics applications, we study a few compounds based on Group 14 elements in this work, namely the dihydrides, dichlorides, and difluorides. Using density functional theory (DFT) calculations, we establish patterns in their properties, including favored coordination chemistry, stability, electronic structure, and dielectric behavior. While a coordination number (CN) of 4 is commonly associated with Group 14 elements, there is a significant deviation from it down the group, with CNs as high as 7 and 8 common in Pb. Further, there is an increase in the relative stability of the ?2 oxidation state as opposed to ?4 when we go from C to Pb, a direct consequence of which is the existence of the di-compounds of C and Si as polymers, whereas the compounds of Ge, Sn, and Pb are strictly 3D crystalline solids. The coordination chemistries are further linked with the band gaps and dielectric constants (divided into two components: the electronic part and the ionic part) of these compounds. We also see that the more stable difluorides and dichlorides have large band gaps and small electronic dielectric constants, and most of the Ge and Sn compounds have remarkably large ionic dielectric constants by virtue of having polar and more flexible bonds. The staggering variation in properties displayed by these parent compounds offers opportunities for designing derivative materials with a desired combination of properties.

Mining Materials Design Rules from Data: The Example of Polymer Dielectrics

“…The electropositive nature of the metal atoms and the high electronegativities of O and F lead to the presence of large dipoles in the organometallics. Aside from being polar, these bonds also display stretching and wagging vibrational modes that are soft in nature, leading to higher IR intensities at low frequencies − and, thus, the highest ϵ ionic values. The organometallics contain no clear demarcations between the different subsets, with high ϵ ionic as well as generally large E gap shown by all.…”

Machine Learning Strategy for Accelerated Design of Polymer Dielectrics

“…In the present work, we focus on the bandgap (E gap ), computed using hybrid electron exchange-correlation functionals, and the electronic ( ϵ elec ), ionic ( ϵ ionic ) and total ( ϵ total = ϵ elec + ϵ ionic ) dielectric constant, computed using density functional perturbation theory, as described in the Methods section. In the case of dielectrics, the bandgap and dielectric constant are the primary properties of interest, generally used in an initial screening stage, regardless of the specific applications 1 30 31 32 .…”

Rational Co‐Design of Polymer Dielectrics for Energy Storage

“…Left) Computed dielectric constants shown vs bandgaps of single‐chain polymers formed from C, Si, Ge, and Sn based units, and (right) the electronic and ionic dielectric constants of compounds of group‐14 elements …”

“…This interesting observation suggests a systematic examination of group‐14 elements, i.e., C, Si, Ge, Sn, and Pb; these systems, in their elemental bulk forms, range from insulators to semiconductors to metals. DFT computations were performed on the hydrides, fluorides, and chlorides based on these elements; the computed ε elec and ε ion of these binaries are shown in Figure b. Compared to C‐ and Si‐based compounds, the ionic dielectric constants of the Ge‐, Pb‐, and especially, Sn‐based materials, are extremely high.…”