skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Combined effect of chemical pressure and valence electron concentration through the electron-deficient Li substitution on the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system

Abstract

Four members of the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system have been prepared by high-temperature reaction method and characterized by X-ray diffractions. All compounds crystallize in the orthorhombic Gd{sub 5}Si{sub 4}-type structure (space group Pnma, Pearson code oP16) with bonding interactions for interslab Ge{sub 2} dimers. The Li substitution for rare-earth elements in the RE{sub 4}LiGe{sub 4} system leads to a combined effect of the increased chemical pressure and the decreased valance electron concentration (VEC), which eventually results in the structure transformation from the Sm{sub 5}Ge{sub 4}-type with all broken interslab Ge–Ge bond for the parental RE{sub 5}Ge{sub 4} to the Gd{sub 5}Si{sub 4}-type structure for the ternary RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system. Site-preference between rare-earth metals and Li is proven to generate energetically the most favorable atomic arrangements according to coloring-problem, and the rationale is provided using both the size-factor and the electronic-factor related, respectively, to site-volume and electronegativity as well as QVAL values. Tight-binding, linear-muffin-tin-orbital (TB-LMTO) calculations are performed to investigate electronic densities of states (DOS) and crystal orbital Hamilton population (COHP) curves. The influence of reduced VEC for chemical bonding including the formation of interslab Ge{sub 2} dimers is alsomore » discussed. The magnetic property measurements prove that the non-magnetic Li substitution leads to the ferromagnetic (FM)-like ground state for Ce{sub 4}LiGe{sub 4} and the co-existence of antiferromagntic (AFM) and FM ground states for Sm{sub 4}LiGe{sub 4}. - Graphical abstract: Reported is a combined effect of the chemical pressure and the reduced VEC caused by the smaller monovalent non-magnetic Li substitution for the larger trivalent magnetic rare-earth metals in the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system. This results in the structure transformation from the Sm{sub 5}Ge{sub 4}-type to the Gd{sub 5}Si{sub 4}-type structure and the changes in magnetic properties. Display Omitted - Highlights: • Four Li-containing intermetallic compounds RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr and Sm) were synthesized. • The combined effect of the chemical pressure and the reduced VEC caused by Li substitution for a rare-earth metal results in the structure transformation. • Electronic structures and magnetic properties of title compounds were thoroughly investigated.« less

Authors:
; ;  [1];  [2];  [3];  [1]
  1. Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 361-763 (Korea, Republic of)
  2. Department of Chemistry, Chungnam National University, Daejeon, Chungnam 305-764 (Korea, Republic of)
  3. Advanced Materials Research Center, Samsung Advanced Institute of Technology, Yongin-si, Gyeonggi-do 446-712 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22274064
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 205; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CRYSTALS; DENSITY; ELECTRONEGATIVITY; GROUND STATES; INTERACTIONS; INTERMETALLIC COMPOUNDS; MAGNETIC PROPERTIES; ORTHORHOMBIC LATTICES; RARE EARTHS; SPACE GROUPS; TRANSFORMATIONS; X-RAY DIFFRACTION

Citation Formats

Nam, Gnu, Jeon, Jieun, Kim, Youngjo, Kwon Kang, Sung, Ahn, Kyunghan, and You, Tae-Soo, E-mail: tsyou@chungbuk.ac.kr. Combined effect of chemical pressure and valence electron concentration through the electron-deficient Li substitution on the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system. United States: N. p., 2013. Web. doi:10.1016/J.JSSC.2013.06.027.
Nam, Gnu, Jeon, Jieun, Kim, Youngjo, Kwon Kang, Sung, Ahn, Kyunghan, & You, Tae-Soo, E-mail: tsyou@chungbuk.ac.kr. Combined effect of chemical pressure and valence electron concentration through the electron-deficient Li substitution on the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system. United States. doi:10.1016/J.JSSC.2013.06.027.
Nam, Gnu, Jeon, Jieun, Kim, Youngjo, Kwon Kang, Sung, Ahn, Kyunghan, and You, Tae-Soo, E-mail: tsyou@chungbuk.ac.kr. Sun . "Combined effect of chemical pressure and valence electron concentration through the electron-deficient Li substitution on the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system". United States. doi:10.1016/J.JSSC.2013.06.027.
@article{osti_22274064,
title = {Combined effect of chemical pressure and valence electron concentration through the electron-deficient Li substitution on the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system},
author = {Nam, Gnu and Jeon, Jieun and Kim, Youngjo and Kwon Kang, Sung and Ahn, Kyunghan and You, Tae-Soo, E-mail: tsyou@chungbuk.ac.kr},
abstractNote = {Four members of the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system have been prepared by high-temperature reaction method and characterized by X-ray diffractions. All compounds crystallize in the orthorhombic Gd{sub 5}Si{sub 4}-type structure (space group Pnma, Pearson code oP16) with bonding interactions for interslab Ge{sub 2} dimers. The Li substitution for rare-earth elements in the RE{sub 4}LiGe{sub 4} system leads to a combined effect of the increased chemical pressure and the decreased valance electron concentration (VEC), which eventually results in the structure transformation from the Sm{sub 5}Ge{sub 4}-type with all broken interslab Ge–Ge bond for the parental RE{sub 5}Ge{sub 4} to the Gd{sub 5}Si{sub 4}-type structure for the ternary RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system. Site-preference between rare-earth metals and Li is proven to generate energetically the most favorable atomic arrangements according to coloring-problem, and the rationale is provided using both the size-factor and the electronic-factor related, respectively, to site-volume and electronegativity as well as QVAL values. Tight-binding, linear-muffin-tin-orbital (TB-LMTO) calculations are performed to investigate electronic densities of states (DOS) and crystal orbital Hamilton population (COHP) curves. The influence of reduced VEC for chemical bonding including the formation of interslab Ge{sub 2} dimers is also discussed. The magnetic property measurements prove that the non-magnetic Li substitution leads to the ferromagnetic (FM)-like ground state for Ce{sub 4}LiGe{sub 4} and the co-existence of antiferromagntic (AFM) and FM ground states for Sm{sub 4}LiGe{sub 4}. - Graphical abstract: Reported is a combined effect of the chemical pressure and the reduced VEC caused by the smaller monovalent non-magnetic Li substitution for the larger trivalent magnetic rare-earth metals in the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system. This results in the structure transformation from the Sm{sub 5}Ge{sub 4}-type to the Gd{sub 5}Si{sub 4}-type structure and the changes in magnetic properties. Display Omitted - Highlights: • Four Li-containing intermetallic compounds RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr and Sm) were synthesized. • The combined effect of the chemical pressure and the reduced VEC caused by Li substitution for a rare-earth metal results in the structure transformation. • Electronic structures and magnetic properties of title compounds were thoroughly investigated.},
doi = {10.1016/J.JSSC.2013.06.027},
journal = {Journal of Solid State Chemistry},
number = ,
volume = 205,
place = {United States},
year = {Sun Sep 15 00:00:00 EDT 2013},
month = {Sun Sep 15 00:00:00 EDT 2013}
}
  • Investigations on phase relationships and crystal structures have been conducted on several ternary rare-earth titanium antimonide systems. The isothermal cross-sections of the ternary RE-Ti-Sb systems containing a representative early (RE=La) and late rare-earth element (RE=Er) have been constructed at 800 deg. C. In the La-Ti-Sb system, the previously known compound La{sub 3}TiSb{sub 5} was confirmed and the new compound La{sub 2}Ti{sub 7}Sb{sub 12} (own type, Cmmm, Z=2, a=10.5446(10) A, b=20.768(2) A, and c=4.4344(4) A) was discovered. In the Er-Ti-Sb system, no ternary compounds were found. The structure of La{sub 2}Ti{sub 7}Sb{sub 12} consists of a complex arrangement of TiSb{sub 6}more » octahedra and disordered fragments of homoatomic Sb assemblies, generating a three-dimensional framework in which La atoms reside. Other early rare-earth elements (RE=Ce, Pr, Nd) can be substituted in this structure type. Attempts to prepare crystals in these systems through use of a tin flux resulted in the discovery of a new Sn-containing pseudoternary phase RETi{sub 3}(Sn{sub x}Sb{sub 1-x}){sub 4} for RE=Nd, Sm (own type, Fmmm, Z=8; a=5.7806(4) A, b=10.0846(7) A, and c=24.2260(16) A for NdTi{sub 3}(Sn{sub 0.1}Sb{sub 0.9}){sub 4}; a=5.7590(4) A, b=10.0686(6) A, and c=24.1167(14) A for SmTi{sub 3}(Sn{sub 0.1}Sb{sub 0.9}){sub 4}). Its structure consists of double-layer slabs of Ti-centred octahedra stacked alternately with nets of the RE atoms; the Ti atoms are arranged in kagome nets. - Graphical abstract: La{sub 2}Ti{sub 7}Sb{sub 12} contains sectioned layers consisting of Ti-centred octahedra linked by corner- and face-sharing.« less
  • New ternary metal borides, EuOs/sub 4/B/sub 4/ and EuIr/sub 4/B/sub 4/, have been synthesized from the elements. The compounds were found to crystallize with the structure type of NdCo/sub 4/B/sub 4/. Effective paramagnetic moments derived from chi/sup -1/vs. T plots over the range 1.8-800 K are in good agreement with theoretical values according to a Hund's rule ground-state /sup 8/S/sub 1/2/ for a free Eu/sup 2 +/ ion. Complete solid solution was found for mixed crystals of CeOs/sub 4/B/sub 4/-CeIr/sub 4/B/sub 4/ (arc melted, quenched, NdCo/sub 4/B/sub 4/-type structure) revealing a positive deviation from Vegard's law. Magnetic susceptibilities were determinedmore » for the temperature range 1.8-1000 K. At high temperature the magnetic properties are characterized by Van Vleck paramagnetism of closely spaced multiplets due to admixture of the excited term J = /sup 7///sub 2/ of the Ce/sup 3 +/F/sub 5///sub 2/ ground state. At lower temperatures the paramagnetic behavior of cerium changes from that of a practically pure Ce/sup 4 +/ state in CeOs/sub 4/B/sub 4/ (..mu../sub eff/ = 0.49 ..mu beta..) to that of a pronounced Ce/sup 3 +/ state in CeIr/sub 4/B/sub 4/ (..mu../sub eff/ = 2.21 ..mu beta..) presumably due to the larger iridium metal framework and/or the higher electron-to-atom ratio. At very low temperatures, less than or equal to 3.5 K, ferromagnetic ordering was observed for CeIr/sub 4/B/sub 4/ and CeIr/sub 3/Os/sub 1/B/sub 4/. For comparison, the magnetic behavior was studied over the range 1.5-300 K of the pseudobinary sections PrOs/sub 4-x/Ir/sub x/B/sub 4/ and SmOs/sub 4-x/Ir/sub x/B/sub 4/. Although a slight negative deviation from Vegard's law was observed, there was practically no change from a valence state of Sm/sup 3 +/ for samarium. On the basis of Miedema's model, a thermodynamic calculation for the valence change (Ce/sup III/ ..-->.. Ce/sup IV/, Eu/sup II/ ..-->.. Eu/sup III/) has been found to be in good accord with the magnetic behavior observed. 7 figures, 4 tables.« less
  • Reactions of rare-earth oxides with TiO 2 were performed in high temperature (650–700 °C) hydrothermal fluids.
  • Two new series of ternary gallides with the chemical formulas (La, Ce, Pr, Nd, Sm)Au/sub x/Ga/sub 4-x/ and (La, Ce, Pr, Nd, Sm)Au/sub 1.5/Ga/sub 2.5/ were synthesized from the elements by arc melting. From x-ray powder diffraction analysis the REAu/sub x/Ga/sub 4-x/ series of compounds was found to be isotypic and crystallize with BaAl/sub 4/ type of structure. At 600/sup 0/C the REAu/sub x/Ga/sub 4-x/ phases of the BaAl/sub 4/ type were observed to be in the thermodynamic equilibrium with a structure variant crystallizing at the composition REAu/sub 1.5/Ga/sub 2.5/ and with a narrow homogeneous range. In case of PrAu/submore » 1.5/Ga/sub 2.5/ the structure type was refined from x-ray single-crystal counter data (CaBe/sub 2/Ge/sub 2/ type, space group P4/nmm, R/sub w/ = 0.046). Gold and gallium atoms were generally found on separate crystallographic sites; however, a statistical distribution of 51% Au + 49% Ga was derived for the 2b sites. /sup 197/Au Moessbauer spectroscopy confirmed the occupational mode of the gold atoms in CeAu/sub 1.5/Ga/sub 2.5/. for the BaAl/sub 4/-type phases, x-ray powder and Moessbauer data revealed preferential occupation of the 4e sites of I4/nmm by gold atoms; practically no Au was observed on the 4d sites. Magnetic susceptibilities were determined over a temperature range extending from 2 to 1100 K. At very low temperatures onset of ferromagnetic ordering is observed for the BaAl/sub 4/-type series of compounds. No superconductivity was encountered down to 2 K.« less