FeAs

FeAs
Name	Iron arsenide
Formula	FeAs
Molar mass	131.73 g·mol−1
Appearance	metallic gray to black solid
Density	6.7 g·cm−3
Melting point	993 °C (decomposes)
Crystal system	orthorhombic
Space group	Pnma

FeAs

FeAs is an inorganic binary compound of iron and arsenic historically studied within inorganic chemistry and solid‑state physics contexts. First characterized during the 19th century, the material bridges research communities including Heinrich Hertz, Ernest Rutherford, and laboratories such as Los Alamos National Laboratory, Max Planck Institute for Chemical Physics of Solids, and Oak Ridge National Laboratory where its properties have been probed alongside related pnictides. Its relevance spans connections to compounds investigated by groups around John B. Goodenough, Alex Müller, and Gerd Binnig through themes common to studies of transition‑metal pnictides, magnetism, and unconventional superconductivity.

Introduction

FeAs is a stoichiometric iron arsenide that crystallizes in an orthorhombic motif and serves as a prototypical member of simple 1:1 iron–pnictogen phases examined by researchers from institutions like Columbia University, Harvard University, and University of Cambridge. Interest in FeAs intensified following discoveries by teams at University of Tokyo, ETH Zurich, and Stanford University into iron‑based superconductors, prompting comparative studies linking FeAs to layered materials explored by groups including Hideo Hosono and Yoshihiko Kitaoka. Experimentalists from facilities such as CERN, Paul Scherrer Institute, and Argonne National Laboratory have applied diffraction and spectroscopy techniques to elucidate its structure and behavior.

Crystal structure

The ambient‑pressure crystal structure of FeAs is orthorhombic (space group Pnma), established via X‑ray and neutron diffraction performed by collaborations at Brookhaven National Laboratory, Rutherford Appleton Laboratory, and ISIS Neutron and Muon Source. The lattice features distorted octahedral coordination of iron by arsenic reminiscent of structural motifs encountered in work from John Goodenough and Alex Müller on perovskites, while sharing connectivity patterns with binary pnictide phases studied at Max Planck Society centers. High‑pressure investigations using diamond anvil cells at Lawrence Berkeley National Laboratory and European Synchrotron Radiation Facility have revealed pressure‑induced distortions related to transitions documented by teams at University of California, Berkeley and University of Tokyo.

Physical and chemical properties

FeAs is a metallic, brittle intermetallic with anisotropic transport properties measured by researchers at MIT, University of Illinois Urbana–Champaign, and Princeton University. Electrical resistivity, thermopower, and heat capacity data collected by groups led by investigators such as Paul C. Canfield and Makoto Nohara show correlations with magnetic ordering phenomena identified in earlier neutron work at Oak Ridge National Laboratory. Chemical reactivity and phase stability have been characterized in studies from Imperial College London and University of Paris‑Saclay, which examined oxidation, sulfidation, and arsenic volatility under conditions explored by teams at Sandia National Laboratories.

Synthesis and preparation

FeAs has been synthesized by solid‑state reactions, chemical vapor transport, and flux methods developed in laboratories at University of California, Santa Barbara, University of Tokyo, and University of Geneva. Early preparations followed metallurgical routes used by researchers at Kurt Mendelssohn‑era teams, while modern protocols utilize sealed ampoules and controlled cooling adopted by experimentalists at University of Oxford and Tohoku University. Chemical vapor transport studies exploiting iodine or tellurium transport agents were reported by groups at University of Stuttgart and University of Amsterdam, and thin‑film deposition efforts leveraging molecular beam epitaxy have been pursued at IBM Research and Bell Labs.

Electronic and magnetic behavior

Electronic structure calculations and angle‑resolved photoemission spectroscopy measurements performed by collaborations including SLAC National Accelerator Laboratory, University College London, and University of Würzburg indicate a complex Fermi surface with contributions from iron d‑states, paralleling motifs explored by theorists such as Philip W. Anderson and Walter Kohn. Magnetically, FeAs exhibits antiferromagnetic order below a Néel temperature determined in experiments at NIMS and Los Alamos National Laboratory, with spin arrangements and excitations probed by neutron scattering groups at Institut Laue–Langevin and Spallation Neutron Source. The interplay of itinerant electrons and localized moments has been analyzed in theoretical work connected to groups at University of Cambridge and University of Tokyo focusing on spin‑density waves and Hund’s coupling.

Applications and research relevance

While FeAs itself is not a commercial superconductor, it serves as a reference system in comparative studies undertaken by research teams at Max Planck Institute for Solid State Research, University of Houston, and Tohoku University to understand superconductivity in iron‑pnictide families discovered by Hideo Hosono and investigated by consortia including Center for Emergent Superconductivity. Investigations at Lawrence Livermore National Laboratory and California Institute of Technology employ FeAs in model studies of magnetotransport, spintronics research at University of California, San Diego and University of Minnesota, and in benchmarking density functional theory carried out by groups at Oak Ridge National Laboratory and Rutgers University.

Safety and handling

Handling FeAs requires protocols consistent with arsenic‑containing materials enforced by occupational safety offices at institutions such as National Institute for Occupational Safety and Health, Health and Safety Executive, and European Chemicals Agency. Laboratories at Johns Hopkins University and Massachusetts Institute of Technology emphasize use of fume hoods, personal protective equipment, and arsenic waste management procedures aligned with guidance from World Health Organization and Occupational Safety and Health Administration to mitigate toxicity and environmental hazards.

Category:Iron compounds Category:Arsenides