Search NASA⌕ Search

DOE OSTI · 1193274

Materials Data on Hf7P4 by Materials Project

Abstract

Hf7P4 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are eight inequivalent Hf sites. In the first Hf site, Hf is bonded in a 5-coordinate geometry to five P atoms. There are four shorter (2.68 Å) and one longer (3.10 Å) Hf–P bond lengths. In the second Hf site, Hf is bonded to five P atoms to form a mixture of distorted edge, face, and corner-sharing HfP5 trigonal bipyramids. There are one shorter (2.62 Å) and four longer (2.68 Å) Hf–P bond lengths. In the third Hf site, Hf is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Hf–P bond distances ranging from 2.69–3.04 Å. In the fourth Hf site, Hf is bonded to five P atoms to form a mixture of distorted edge, face, and corner-sharing HfP5 trigonal bipyramids. There are a spread of Hf–P bond distances ranging from 2.57–2.71 Å. In the fifth Hf site, Hf is bonded in a 4-coordinate geometry to four P atoms. There are a spread of Hf–P bond distances ranging from 2.61–2.87 Å. In the sixth Hf site, Hf is bonded in a 4-coordinate geometry to five P atoms. There are a spread of Hf–P bond distances ranging from 2.69–3.29 Å. In the seventh Hf site, Hf is bonded in a square co-planar geometry to four P atoms. There are two shorter (2.71 Å) and two longer (2.73 Å) Hf–P bond lengths. In the eighth Hf site, Hf is bonded in a distorted square co-planar geometry to four P atoms. There are two shorter (2.60 Å) and two longer (2.85 Å) Hf–P bond lengths. There are four inequivalent P sites. In the first P site, P is bonded in a 7-coordinate geometry to nine Hf atoms. In the second P site, P is bonded in a 9-coordinate geometry to nine Hf atoms. In the third P site, P is bonded to seven Hf atoms to form a mixture of distorted edge and corner-sharing PHf7 pentagonal bipyramids. In the fourth P site, P is bonded in a 8-coordinate geometry to eight Hf atoms.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

2020-07-15. Materials Data on Hf7P4 by Materials Project. https://doi.org/10.17188/1193274

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related reports

Cyclic moisture reactivation of calcium sorbents for long duration thermochemical energy storage

The transition to a flexible and reliable energy infrastructure, using electro-thermal energy generation technologies such as geothermal, concentrated solar power, and nuclear, usually demands simultaneous advancement of thermal energy storage (TES) to support on-demand electricity generation and industrial applications while mitigating the inherent intermittency of renewable energy sources and power outages from direct energy generation. Among TES technologies, thermochemical energy storage (TCES) based on calcium looping emerges as a compelling high-power energy storage candidate due to its high reaction enthalpy, compatibility with elevated operating temperatures, and abundance of low-cost materials. However, the long-term durability of calcium-based sorbents for TCES is hindered by surface sintering and particle aggregation, leading to performance degradation over repeated thermal cycles. This study explores a moisture hydration-based strategy to regenerate a degraded calcium sorbent and mitigate performance degradation for long duration TCES. The addition of moisture transforms calcium oxide into calcium hydroxide and produces intercalation water layers, associated with a regenerated surface area and reduced calcium oxide crystallite size. Both these effects are beneficial in restoring the sorbents' reactivity for carbonization. Additionally, an optimized hydration-assisted reactivation protocol balances the recovered energy storage capacity with heating penalty required for moisture removal from hydrated samples, resulting in an enhanced energy storage capacity up to 176% compared to benchmark sorbents that undergo cycling without reactivation after 60 cycles. In conclusion, these results highlight the potential of hydration-assisted reactivation to enhance the long-term performance of TCES, providing an effective pathway to advancing electro-thermal storage technologies.

36 MATERIALS SCIENCE↗