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Energy Relevant Materials: Investigations Based on First Principle

Technical Report:

Abstract

Energy production, storage and efficient usage are all crucial factors for environmentally sound and sustainable future technologies. One important question concerns the refrigeration industry, where the energy efficiency of the presently used technologies is at best 40% of the theoretical Carnot limit. Magnetic refrigerators offer a modern low-energy demand and environmentally friendly alternative. Iron phosphide based materials have been proposed to be amongst the most promising candidates for working body of magnetic refrigerators. Hydrogen is one of the central elements on the most promising sources of renewable energy. Considerable international research focuses on finding good solid state materials for hydrogen storage. On the other hand, hydrogen gas is obtained from hydrogen containing chemical compounds, which after breaking the chemical bounds usually yield to a mixture of different gases. Palladium-silver alloys are frequently used for hydrogen separation membranes for producing purified hydrogen gas. All these applications need a fundamental understanding of the structural, magnetic, chemical and thermophysical properties of the involved solid state materials. In the present thesis ab initio electronic structure methods are used to study the crystallographic and magnetic properties of Fe{sub 2}P based magneto-caloric compounds and the thermophysical properties of Pd-Ag binary alloys. Lattice stability of pure Fe{sub  More>>
Publication Date:
Nov 15, 2010
Product Type:
Technical Report
Report Number:
KTH-MSE-10-48
Resource Relation:
Other Information: Thesis or Dissertation; TH: Licentiate thesis (TeknLic); 69 refs., 13 figs., 4 tabs.
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; MATERIALS; MAGNETIC REFRIGERATORS; HYDROGEN STORAGE; IRON PHOSPHIDES; PALLADIUM ALLOYS; SILVER ADDITIONS; ENERGY EFFICIENCY; ELECTRONIC STRUCTURE; MICROSTRUCTURE; CRYSTAL STRUCTURE
OSTI ID:
1005372
Research Organizations:
Royal Inst. of Technology, Stockholm (Sweden). School of Industrial Engineering and Management, Dept. of Materials Science and Engineering
Country of Origin:
Sweden
Language:
English
Other Identifying Numbers:
Other: ISBN 978-91-7415-752-9; TRN: SE1107034
Availability:
Available from URI: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-25050
Submitting Site:
SWD
Size:
44 p. pages
Announcement Date:
Feb 28, 2011

Technical Report:

Citation Formats

Delczeg-Czirjak, Erna-Krisztina. Energy Relevant Materials: Investigations Based on First Principle. Sweden: N. p., 2010. Web.
Delczeg-Czirjak, Erna-Krisztina. Energy Relevant Materials: Investigations Based on First Principle. Sweden.
Delczeg-Czirjak, Erna-Krisztina. 2010. "Energy Relevant Materials: Investigations Based on First Principle." Sweden.
@misc{etde_1005372,
title = {Energy Relevant Materials: Investigations Based on First Principle}
author = {Delczeg-Czirjak, Erna-Krisztina}
abstractNote = {Energy production, storage and efficient usage are all crucial factors for environmentally sound and sustainable future technologies. One important question concerns the refrigeration industry, where the energy efficiency of the presently used technologies is at best 40% of the theoretical Carnot limit. Magnetic refrigerators offer a modern low-energy demand and environmentally friendly alternative. Iron phosphide based materials have been proposed to be amongst the most promising candidates for working body of magnetic refrigerators. Hydrogen is one of the central elements on the most promising sources of renewable energy. Considerable international research focuses on finding good solid state materials for hydrogen storage. On the other hand, hydrogen gas is obtained from hydrogen containing chemical compounds, which after breaking the chemical bounds usually yield to a mixture of different gases. Palladium-silver alloys are frequently used for hydrogen separation membranes for producing purified hydrogen gas. All these applications need a fundamental understanding of the structural, magnetic, chemical and thermophysical properties of the involved solid state materials. In the present thesis ab initio electronic structure methods are used to study the crystallographic and magnetic properties of Fe{sub 2}P based magneto-caloric compounds and the thermophysical properties of Pd-Ag binary alloys. Lattice stability of pure Fe{sub 2}P and the effect of Si doping on the phase stability are presented. In contrast to the observation, for the ferromagnetic state the body centered orthorhombic structure (bco, space group Imm2) is predicted to have lower energy than the hexagonal structure (hex, space group P62m). The zero-point spin fluctuation energy difference is found to be large enough to stabilize the hex phase. For the paramagnetic state, the hex structure is shown to be the stable phase and the computed total energy versus composition indicates a hex to bco crystallographic phase transition with increasing Si content. The magneto-structural effects and the mechanisms responsible for the structural phase transition are discussed in details. The magnetic properties of Fe{sub 2}P can be subtly tailored by Mn doping. It has been shown experimentally that Mn atoms preferentially occupy one of the two different Fe sites of Fe{sub 2}P. Theoretical results for the Mn site occupancy in MnFeP{sub 1-x}Si{sub x} are presented. The single crystal and polycrystalline elastic constants and the Debye temperature of Pd{sub 1-x}Ag{sub x} binary alloys are calculated for the whole range of concentration, 0 < x < 1. It is shown that the variation of the elastic parameters of Pd-Ag alloys with chemical composition strongly deviates from the simple expected trend. The complex electronic origin of these anomalies is demonstrated. Within the present thesis, all relaxed crystal structures are obtained using the Projector Augmented Wave full-potential method. The chemical and magnetic disorder is treated using the Exact Muffin-Tin Orbitals method in combination with the Coherent Potential Approximation. The paramagnetic phase is modeled by the Disordered Local Magnetic Moments approach}
place = {Sweden}
year = {2010}
month = {Nov}
}