Surface, interface, and temperature effects on the phase separation and nanoparticle self assembly of bi-metallic Ni0.5Ag0.5: A molecular dynamics study

Ryan H. Allaire, Abhijeet Dhakane, Reece Emery, P. Ganesh, Philip D. Rack, Lou Kondic, Linda Cummings, Miguel Fuentes-Cabrera

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Classical molecular dynamics (MD) simulations were used to investigate how free surfaces, as well as supporting substrates, affect phase separation in a NiAg alloy. Bulk samples, droplets, and droplets deposited on a graphene substrate were investigated at temperatures that spanned regions of interest in the bulk NiAg phase diagram, i.e., miscible and immiscible liquid, liquid-crystal, and crystal-crystal regions. Using MD simulations to cool down a bulk sample from 3000 K to 800 K, it was found that phase separation below 2400 K takes place in agreement with the phase diagram. When free surface effects were introduced, phase separation was accompanied by a core-shell transformation: spherical droplets created from the bulk samples became core-shell nanoparticles with a shell made mostly of Ag atoms and a core made of Ni atoms. When such droplets were deposited on a graphene substrate, the phase separation was accompanied by Ni layering at the graphene interface and Ag at the vacuum interface. Thus, it should be possible to create NiAg core-shell and layer-like nanostructures by quenching liquid NiAg samples on tailored substrates. Furthermore, interesting bimetallic nanoparticle morphologies might be tuned via control of the surface and interface energies and chemical instabilities of the system.

Original languageEnglish
Article number1040
JournalNanomaterials
Volume9
Issue number7
DOIs
StatePublished - Jul 2019

Funding

DOE Discretionary allocation at Titan supercomputer, at ORNL.P.D.R. acknowledges support from NSF CBET-1603780. A.D. performed research under an appointment to the Higher Education Research Experiences at the Oak Ridge National Laboratory, administered by the Oak Ridge Institute for Science and Education. R.H.A. and L.K. acknowledge support as a result of the NSF Grant No. CBET 1604351. AuAthuothroCroCnotrnitbruibtiuotniosn: Cs:oCnocenpcteupatluizaalitzioanti,o Mn,.FM.-.CF..-,CL..,KL..,KP..,DP..RD..,Ra.n, danLd.CL..;Cm.;emtheotdhooldooglyo,gMy,.MF.-.CF..-,CR.,.HR..AH..,AA.,.DA..,D., R.E., and P.G.; software, R.H.A.; validation, R.H.A., R.E., and A.D.; formal analysis, R.H.A., R.E., and A.D; investigation, R.H.A. and R.E.; resources, M.F.-C., L.K., P.D.R., and L.C.; data curation, R.H.A.; writing—original investigation, R.H.A. and R.E.; resources, M.F.-C., L.K., P.D.R., and L.C.; data curation, R.H.A.; writing—original draft preparation, R.H.A., M.F.-C., L.K., and P.D.R.; writing—review and editing, R.H.A., M.F.-C., L.K., P.D.R., draft preparation, R.H.A., M.F.-C., L.K., and P.D.R.; writing—review and editing, R.H.A., M.F.-C., L.K., P.D.R., L.C., and P.G.; visualization, R.H.A.; supervision, M.F.-C., L.K., and P.D.R.; project administration, M.F.-C., L.K., and P.D.R.; funding acquisition, M.F.-C., L.K., P.D.R., and L.C. Funding: R.H.A. was supported by a DOE Office of the Science Graduate Student Research Program. This research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. Computational resources used a Director Discretionary allocation at Titan supercomputer, at ORNL. P.D.R. research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User acknowledges support from NSF CBET-1603780. A.D. performed research under an appointment to the Higher Facility. Computational resources used a Director Discretionary allocation at Titan supercomputer, at ORNL. P.D.R. acknowledges support from NSF CBET-1603780. A.D. performed research under an appointment to the Higher Education Research Experiences at the Oak Ridge National Laboratory, administered by the Oak Ridge Acknowledgments: We would like to thank Jason Fowlkes and David Garfinkel for insightful discussions. Institute for Science and Education. R.H.A. and L.K. acknowledge support as a result of the NSF Grant No. CBET 1604351.Conflicts of Interest: The authors declare no conflict of interest.

Keywords

  • Core-shell nanoparticles
  • Metallic nanoparticles
  • Molecular dynamics simulations
  • Phase separation
  • Self-assembly

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