Stability of the 1144 phase in iron pnictides

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2018-03-01
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Song, B. Q.
Nguyen, Manh Cuong
Wang, Cai-Zhuang
Ho, Kai-Ming
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Ames National Laboratory

Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.

For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.

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Physics and Astronomy
Physics and astronomy are basic natural sciences which attempt to describe and provide an understanding of both our world and our universe. Physics serves as the underpinning of many different disciplines including the other natural sciences and technological areas.
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Ames National LaboratoryPhysics and Astronomy
Abstract

A series of iron arsenides (e.g., CaRbFe4As4, SrCsFe4As4) have been discovered recently, and have provoked a rise in superconductor searches in a different phase, known as the 1144 phase. For the presence of various chemical substitutions, it is believed that more 1144 compounds remain to be discovered. In this work, we perform general model analysis as well as scenario calculation on a basis of density functional theory to investigate phase stability in a variety of compounds. We predict that the 1144-type phase could be stabilized in EuKFe4As4, EuRbFe4As4, EuCsFe4As4, CaCsFe4P4, SrCsFe4P4, BaCsFe4P4, InCaFe4As4, InSrFe4As4, etc. Remarkably, it involves rare earths, trivalence elements (e.g., indium) and iron phosphides, which greatly expands the range of its existence and suggests a promising prospect for experimental synthesis. In addition, we find that the formation of many random doping compounds (e.g., Ba0.5Cs0.5Fe2As2, Ba0.5R0.5Fe2As2) is driven by entropy and could be annealed to a 1144-type phase. Eventually, we plot a phase diagram about two structural factors Delta a and Delta c, giving a bird's-eye view of stability of various 1144 compounds.

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