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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on LaP5 by Materials Project

LaP5 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are two inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a 8-coordinate geometry to eight P+0.60- atoms. There are a spread of La–P bond distances ranging from 3.03–3.13 Å. In the second La3+ site, La3+ is bonded in a 8-coordinate geometry to eight P+0.60- atoms. There are a spread of La–P bond distances ranging from 3.01–3.15 Å. There are six inequivalent P+0.60- sites. In the first P+0.60- site, P+0.60- is bonded to one La3+ and three P+0.60- atoms to form PLaP3 tetrahedra that share corners with four equivalent PLa2P2 tetrahedra and an edgeedge with one PLaP3 tetrahedra. There are a spread of P–P bond distances ranging from 2.18–2.23 Å. In the second P+0.60- site, P+0.60- is bonded in a 4-coordinate geometry to two equivalent La3+ and two P+0.60- atoms. There are one shorter (2.19 Å) and one longer (2.23 Å) P–P bond lengths. In the third P+0.60- site, P+0.60- is bonded to one La3+ and three P+0.60- atoms to form distorted PLaP3 tetrahedra that share corners with five PLa2P2 tetrahedra and an edgeedge with one PLaP3 tetrahedra. The P–P bond length is 2.23 Å. In the fourth P+0.60- site, P+0.60- is bonded to two equivalent La3+ and two P+0.60- atoms to form distorted PLa2P2 tetrahedra that share corners with eleven PLaP3 tetrahedra and an edgeedge with one PLa2P2 tetrahedra. In the fifth P+0.60- site, P+0.60- is bonded in a distorted rectangular see-saw-like geometry to two equivalent La3+ and two equivalent P+0.60- atoms. In the sixth P+0.60- site, P+0.60- is bonded to two equivalent La3+ and two equivalent P+0.60- atoms to form distorted corner-sharing PLa2P2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Side-Chain and Ring-Size Effects on Permeability in Artificial Water Channels

Artificial water channels (AWCs) have emerged as a promising framework for stable water permeation, with water transport rates comparable to aquaporins (3.4–40.3 × 10 8 H 2 O/channel/s). In this study, we probe the influence of ring-size and side-chain length on the water permeability observed within a class of AWCs termed ligand-appended pillar[n]arenes (LAPs) that have an adjustable ring-size (m) and side-chain length (n). Through all-atom molecular dynamics simulations, we calculate the permeability of these channels using the collective diffusion model and find their permeabilities. We characterize the mechanistic influence of pillar[n]arene ring-size and side-chain length on the channel water permeability by analyzing the characteristics of the internal permeating water-wire and the surrounding channel structure. We observe that water permeability decreases as a function of increasing ring-size due to increases in hydrophilic contacts between the permeating water-wire and the oxygen groups on the channel wall. Further, we observe an increase in water permeability as a function of side-chain length due to increased partitioning of the channel terminal groups into the hydrophilic blocks of the surrounding bilayer. For the LAP6 channel, with increase in side-chain length, the distance between terminal groups increases and leads to an increase in pore size, thereby enhancing water permeability. In the case of LAP5, as side-chain length increases, the channel displays a compensatory effect between tilt and bend angle due to the flexible side-chains. Such flexibility leads to higher terminal group partitioning in the hydrophilic blocks of the bilayer and extends the permeating water-wire. Furthermore, this increase in water-wire length and hydrophilic block access overcomes the nonmonotonic pore size trend in pillar[5]arene channels.

36 MATERIALS SCIENCE↗