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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Generic FEPs Catalogue and Salt Knowledge Archive

This report describes the development of a comprehensive catalogue of generic features, events, and processes (FEPs) that are potentially important for the post-closure performance of a repository for high-level radioactive waste (HLW) and spent nuclear fuel (SNF) in salt (halite) host rock. The FEPs and other supporting information have been entered into a “SaltFEP” Database. The generic salt repository FEPs include consideration of relevant FEPs from a number of U.S., Dutch, German, and international FEP lists and should be a suitable starting point for any repository program in salt host rock. The salt FEP catalogue and database employ a FEP classification matrix approach that is based on the concept that a FEP is typically a process or event acting upon or within a feature. The FEP matrix provides a two-dimensional structure consisting of a Features/Components axis that defines the “rows” and a Processes/Events axis that defines the “columns” of the matrix. The design of the FEP classification matrix is consistent with repository performance assessment – the Features/Components axis is organized vertically to generally correspond to the direction of potential radionuclide migration (from the waste to the biosphere) and the Processes/Events axis is designed to represent the common two-way couplings between thermal processes and other processes (such as thermal-mechanical or thermal-hydrologic processes). Related FEPs can be easily identified – related FEPs will typically be grouped in a single matrix cell or aligned along a common row (Feature/Component) or column (Process/Event). The online SaltFEP database can be downloaded from www.saltfep.org. It contains the FEP matrix, the FEPs, and the associated processes for each FEP. It provides a starting point to create and document site-specific individual FEPs. Furthermore, the FEP matrix is connected to the Salt Knowledge Archive (SKA), a database of about 20,000 references and documents representing the historical knowledge on radioactive disposal in salt. This work is the result of an ongoing collaboration between researchers in the U.S., the Netherlands, and Germany, and supports the NEA Salt Club Mandate. It builds upon prior work which is documented.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Orbital-selective Mott phase and non-Fermi liquid in FePS 3

The layered metal phosphorous trisulfide FePS 3 is reported to be a Mott insulator at ambient conditions and to undergo structural and insulator-metal phase transitions under pressure. However, the character of the resulting metallic states has not been understood clearly so far. Here, we theoretically study the phase transitions of FePS 3 using first-principles methods based on density functional theory and embedded dynamical mean field theory. We find that the Mott transition in FePS 3 can be orbital selective, with t 2g states undergoing a correlation-induced insulator-to-metal transition while e g states remain gapped. We show that this orbital-selective Mott phase, which occurs only when nonhydrostatic pressure is used, is a bad metal (or non-Fermi liquid) with large fluctuating moments due to Hund's coupling. Further application of pressure increases the crystal-field splitting and converts the system to a conventional Fermi liquid with low-spin configurations dominant. Finally, our results show that FePS 3 is an example of a system that realizes an orbital-selective Mott phase, allowing tuning between correlated and uncorrelated metallic properties in an accessible pressure range (≤ 18 GPa).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

The Hard Ferromagnetism in FePS 3 Induced by Non‐Magnetic Molecular Intercalation

Abstract Manipulating the magnetic ground states of 2D magnets is a focal point of recent research efforts. Various methods have demonstrated efficacy in modulating the magnetic properties inherent to van der Waals (vdW) magnetic systems. Herein, the emergence of robust anisotropic ferromagnetism within antiferromagnetic FePS 3 is unveiled via intercalation with non‐magnetic pyridinium ions. A one‐step ion exchange reaction facilitates the formation of energetically favorable B‐phase and metastable P‐phase. Notably, both B‐ and P‐phases manifest hard ferromagnetic behavior, featuring substantial unsaturated coercive fields (>7 T) and high Curie temperatures (72–87 K). First‐principles calculations elucidate the pivotal role of electron transfer from pyridinium ions to FePS 3 in engineering magnetic exchange interactions. Calculated effective spin Hamiltonian corroborates the observed hard ferromagnetism in intercalated FePS 3 . This study offers crucial insights into hard magnetism in intercalated vdW materials, thereby presenting promising avenues for 2D vdW magnet‐based magnetic devices.

Ou, Yunbo↗
DOE OSTI2021

Low-Frequency Electronic Noise in Quasi-2D van der Waals Antiferromagnetic Semiconductor FePS 3 —Signatures of Phase Transitions

Here, low-frequency current fluctuations, i.e., noise, in the quasi-2D van der Waals antiferromagnetic semiconductor FePS 3 with the electronic bandgap of 1.5 eV is investigated. The electrical and noise characteristics of the p-type, highly resistive, thin films of FePS 3 are measured at different temperatures. The noise spectral density is of the 1/f-type over most of the examined temperature range but reveals well-defined Lorentzian bulges, and increases strongly near the Néel temperature T N =118 K (f is the frequency). Intriguingly, the noise spectral density attains its minimum at temperature T≈200 K, which is attributed to an interplay of two opposite trends in noise scaling—one for semiconductors and another for materials with the phase transitions. The Lorentzian corner frequencies reveal unusual dependence on temperature and bias voltage, suggesting that their origin is different from the generation—recombination noise in conventional semiconductors. The obtained results are important for proposed applications of antiferromagnetic semiconductors in spintronic devices. They also attest to the power of the noise spectroscopy for monitoring various phase transitions.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Metal Site Substitution and Role of the Dimer on Symmetry Breaking in FePS 3 and CrPS 4 under Pressure

We combine infrared absorption, Raman scattering, and diamond anvil cell techniques to explore the properties of FePS 3 and CrPS 4 under pressure, comparing our findings with a symmetry analysis, lattice dynamics calculations, and an examination of the energy landscape. Although these complex chalcogenides are considered to be members of the same family of materials, they display remarkably different phase progressions on account of the metal center orbital filling, character of the P–P linkage, layer corrugation, and differing size of the van der Waals gap. Here, we discuss the space group progressions, structure–property relations, and development of pressure-induced metallicity in terms of the competition between local and long-range symmetry transformations and structural distortion pathways. These findings place the properties of FePS 3 and CrPS 4 on a firm foundation for work under strain control and in the single layer limit.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeP by Materials Project

FeP is Modderite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Fe3+ is bonded to six equivalent P3- atoms to form a mixture of distorted edge, face, and corner-sharing FeP6 octahedra. The corner-sharing octahedra tilt angles range from 43–57°. There are a spread of Fe–P bond distances ranging from 2.22–2.33 Å. P3- is bonded in a 6-coordinate geometry to six equivalent Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(FeP)2 by Materials Project

U(FeP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. U is bonded in a 8-coordinate geometry to eight equivalent Fe and eight equivalent P atoms. All U–Fe bond lengths are 3.01 Å. All U–P bond lengths are 2.93 Å. Fe is bonded to four equivalent U and four equivalent P atoms to form a mixture of distorted edge, face, and corner-sharing FeU4P4 tetrahedra. All Fe–P bond lengths are 2.23 Å. P is bonded in a 9-coordinate geometry to four equivalent U, four equivalent Fe, and one P atom. The P–P bond length is 2.32 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Observation of Giant Optical Linear Dichroism in a Zigzag Antiferromagnet FePS 3

Direct optical probing of the antiferromagnetic order parameter in atomically thin samples is challenging, for example, via magneto-optical spectroscopy, due to the lack of net magnetization. Here, we report zigzag-antiferromagnetism (AFM) induced optical linear dichroism (LD) in layered transition-metal thiophosphate FePS3 down to the monolayer limit. The observed LD is giant despite having the optical wave vector parallel to the Neel vector. The LD is at least one order of magnitude larger than those reported in other antiferromagnetic systems, where the optical wave vector is orthogonal to the Neel vector. The large LD enables the probe of 60 degrees orientated zigzag-AFM domains. The optical anisotropy in FePS 3 originates from an electronic anisotropy associated with the zigzag direction of the AFM order and is independent of the spin-pointing direction. Furthermore, our findings point to a new optical approach for the investigation and control of zigzag or stripe magnetic order in strongly correlated systems.

2D magnet↗
DOE OSTI2025

Tuning magnetism in Ising-type van der Waals magnet FePS 3 by lithium intercalation

Recently, layered transition metal thiophosphate MPX 3 (M = transition metals, X = S or Se) have gained significant attention because of their rich magnetic, optical, and electronic properties. Specifically, the diverse magnetic structures and the robustness of magnetism in the two-dimensional (2D) limit have made them prominent candidates to study 2D magnetism. Numerous efforts such as substitutions and interlayer intercalations have been adopted to tune the magnetic properties of these materials, which has greatly deepened the understanding of the underlying mechanisms that govern the properties. In this work, we focus on modifying the magnetism of Ising-type antiferromagnet FePS 3 using electrochemical lithium intercalation. Furthermore, our work demonstrate the effectiveness of electrochemical intercalation as a controllable tool to modulating magnetism, including tuning magnetic ordering temperature and inducing low temperature spin-glass state, offering an approach for implementing this material into applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on Eu(FeP)2 by Materials Project

EuFe2P2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Eu2+ is bonded in a body-centered cubic geometry to eight equivalent P3- atoms. All Eu–P bond lengths are 3.13 Å. Fe2+ is bonded to four equivalent P3- atoms to form a mixture of edge and corner-sharing FeP4 tetrahedra. All Fe–P bond lengths are 2.20 Å. P3- is bonded in a 4-coordinate geometry to four equivalent Eu2+ and four equivalent Fe2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(FeP)2 by Materials Project

CaFe2P2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca2+ is bonded in a body-centered cubic geometry to eight equivalent P3- atoms. All Ca–P bond lengths are 3.05 Å. Fe2+ is bonded to four equivalent P3- atoms to form a mixture of edge and corner-sharing FeP4 tetrahedra. All Fe–P bond lengths are 2.20 Å. P3- is bonded in a 4-coordinate geometry to four equivalent Ca2+ and four equivalent Fe2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La(FeP)2 by Materials Project

LaFe2P2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. La2+ is bonded in a body-centered cubic geometry to eight equivalent P3- atoms. All La–P bond lengths are 3.16 Å. Fe2+ is bonded to four equivalent P3- atoms to form a mixture of corner and edge-sharing FeP4 tetrahedra. All Fe–P bond lengths are 2.20 Å. P3- is bonded in a 4-coordinate geometry to four equivalent La2+ and four equivalent Fe2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(FeP)2 by Materials Project

CeFe2P2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ce is bonded in a 8-coordinate geometry to eight equivalent Fe and eight equivalent P atoms. All Ce–Fe bond lengths are 3.18 Å. All Ce–P bond lengths are 3.06 Å. Fe is bonded to four equivalent Ce and four equivalent P atoms to form a mixture of distorted face, edge, and corner-sharing FeCe4P4 tetrahedra. All Fe–P bond lengths are 2.20 Å. P is bonded in a 4-coordinate geometry to four equivalent Ce and four equivalent Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FePS by Materials Project

FeSP is Spinel-like structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Fe3+ is bonded to three equivalent P1- and three equivalent S2- atoms to form FeP3S3 octahedra that share corners with eight equivalent FeP3S3 octahedra, corners with three equivalent PFe3S tetrahedra, corners with three equivalent SFe3P tetrahedra, and edges with two equivalent FeP3S3 octahedra. The corner-sharing octahedra tilt angles range from 54–62°. There are one shorter (2.28 Å) and two longer (2.30 Å) Fe–P bond lengths. There are two shorter (2.20 Å) and one longer (2.21 Å) Fe–S bond lengths. P1- is bonded to three equivalent Fe3+ and one S2- atom to form PFe3S tetrahedra that share corners with three equivalent FeP3S3 octahedra, corners with four equivalent PFe3S tetrahedra, corners with nine equivalent SFe3P tetrahedra, and an edgeedge with one PFe3S tetrahedra. The corner-sharing octahedra tilt angles range from 68–72°. The P–S bond length is 2.25 Å. S2- is bonded to three equivalent Fe3+ and one P1- atom to form SFe3P tetrahedra that share corners with three equivalent FeP3S3 octahedra, corners with four equivalent SFe3P tetrahedra, corners with nine equivalent PFe3S tetrahedra, and an edgeedge with one SFe3P tetrahedra. The corner-sharing octahedra tilt angles range from 75–77°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeP(HO2)2 by Materials Project

FeH2PO4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of four hydrogen molecules and one FeHPO4 framework. In the FeHPO4 framework, Fe3+ is bonded to one H and four O2- atoms to form distorted FeHO4 trigonal bipyramids that share corners with four equivalent PO4 tetrahedra. The Fe–H bond length is 1.62 Å. There are a spread of Fe–O bond distances ranging from 1.89–1.92 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four equivalent FeHO4 trigonal bipyramids. There is one shorter (1.53 Å) and three longer (1.55 Å) P–O bond length. H is bonded in a distorted single-bond geometry to one Fe3+ atom. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Fe3+ and one P5+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Fe3+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one P5+ atom.

36 MATERIALS SCIENCE↗