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Full-Text Articles in Physics

Energetics Of Cu Adsorption And Intercalation At Graphite Step Edges, Yong Han, Ann Lii-Rosales, Michael C. Tringides, James W. Evans, Patricia A. Thiel Mar 2019

Energetics Of Cu Adsorption And Intercalation At Graphite Step Edges, Yong Han, Ann Lii-Rosales, Michael C. Tringides, James W. Evans, Patricia A. Thiel

Chemistry Publications

To assess the energetics of Cu intercalation on defective graphite, the chemical potentials and binding energies for Cu at graphite step edges are calculated for three main configurations: an isolated atom, a chain, and an atom attached to a chain. As expected, for Cu interacting directly with a graphite step edge, the strength of interaction depends on the stability of the step, with Cu binding more strongly at a less-stable step. However, the relationship is reversed when considering binding of a Cu atom attached to a chain. Taken together, these trends mean that if the graphite step is less stable ...


Defect-Mediated, Thermally-Activated Encapsulation Of Metals At The Surface Of Graphite, Yinghui Zhou, Ann Lii-Rosales, Minsung Kim, Mark Wallingford, Dapeng Jing, Michael C. Tringides, Cai-Zhuang Wang, Patricia A. Thiel Feb 2018

Defect-Mediated, Thermally-Activated Encapsulation Of Metals At The Surface Of Graphite, Yinghui Zhou, Ann Lii-Rosales, Minsung Kim, Mark Wallingford, Dapeng Jing, Michael C. Tringides, Cai-Zhuang Wang, Patricia A. Thiel

Chemistry Publications

We show that 3 metals – Dy, Ru, and Cu – can form multilayer intercalated (encapsulated) islands at the graphite (0001) surface if 2 specific conditions are met: Defects are introduced on the graphite terraces to act as entry portals, and the metal deposition temperature is well above ambient. Focusing on Dy as a prototype, we show that surface encapsulation is much different than bulk intercalation, because the encapsulated metal takes the form of bulk-like rafts of multilayer Dy, rather than the dilute, single-layer structure known for the bulk compound. Carbon-covered metallic rafts even form for relatively unreactive metals (Ru and Cu ...


Polar Intermetallics Pr5co2ge3 And Pr7co2ge4 With Planar Hydrocarbon‐Like Metal Clusters, Qisheng Lin, Kaiser Aguirre, Scott M. Saunders, Timothy A. Hackett, Yong Liu, Valentin Taufour, Durga Paudyal, Sergey L. Bud’Ko, Paul C. Canfield, Gordon J. Miller Aug 2017

Polar Intermetallics Pr5co2ge3 And Pr7co2ge4 With Planar Hydrocarbon‐Like Metal Clusters, Qisheng Lin, Kaiser Aguirre, Scott M. Saunders, Timothy A. Hackett, Yong Liu, Valentin Taufour, Durga Paudyal, Sergey L. Bud’Ko, Paul C. Canfield, Gordon J. Miller

Chemistry Publications

Planar hydrocarbon‐like metal clusters may foster new insights linking organic molecules with conjugated π–π bonding interactions and inorganic structures in terms of their bonding characteristics. However, such clusters are uncommon in polar intermetallics. Herein, we report two polar intermetallic phases, Pr5Co2Ge3 and Pr7Co2Ge4, both of which feature such planar metal clusters, namely, ethylene‐like [Co2Ge4] clusters plus the concatenated forms and polyacene‐like [Co2Ge2]n ribbons in Pr5Co2Ge3, and 1,2,4,5‐tetramethylbenzene‐like [Co4Ge6] cluster in Pr7Co2Ge4. Just as in the related planar organic structures, these metal–metalloid species are dominated by covalent bonding interactions. Both ...


Β-Mn-Type Co8+Xzn12–X As A Defect Cubic Laves Phase: Site Preferences, Magnetism, And Electronic Structure, Weiwei Xie, Srinvasa Timmaiah, Jagat Lamal, Jing Liu, Thomas W. Heitmann, Dante Quirinale, A. I. Goldman, Vitalij K. Pecharsky, Gordon J. Miller Jan 2013

Β-Mn-Type Co8+Xzn12–X As A Defect Cubic Laves Phase: Site Preferences, Magnetism, And Electronic Structure, Weiwei Xie, Srinvasa Timmaiah, Jagat Lamal, Jing Liu, Thomas W. Heitmann, Dante Quirinale, A. I. Goldman, Vitalij K. Pecharsky, Gordon J. Miller

Chemistry Publications

The results of crystallographic analysis, magnetic characterization, and theoretical assessment of β-Mn-type Co–Zn intermetallics prepared using high-temperature methods are presented. These β-Mn Co–Zn phases crystallize in the space group P4132 [Pearson symbol cP20; a = 6.3555(7)–6.3220(7)], and their stoichiometry may be expressed as Co8+xZn12–x [1.7(2) < x < 2.2(2)]. According to a combination of single-crystal X-ray diffraction, neutron powder diffraction, and scanning electron microscopy, atomic site occupancies establish clear preferences for Co atoms in the 8c sites and Zn atoms in the 12d sites, with all additional Co atoms replacing some Zn atoms, a result that can be rationalized by electronic structure calculations. Magnetic measurements and neutron powder diffraction of an equimolar Co:Zn sample confirm ferromagnetism in this phase with a Curie temperature of ∼420 K. Neutron powder diffraction and electronic structure calculations using the local spin density approximation indicate that the spontaneous magnetization of this phase arises exclusively from local moments at the Co atoms. Inspection of the atomic arrangements of Co8+xZn12–x reveals that the β-Mn aristotype may be derived from an ordered defect, cubic Laves phase (MgCu2-type) structure. Structural optimization procedures using the Vienna ab initio simulation package (VASP) and starting ...