title: Solute segregation and deviation from bulk thermodynamics at nanoscale crystalline defects.
abstract: It has long been known that solute segregation at crystalline defects can have profound effects on material properties. Nevertheless, quantifying the extent of solute segregation at nanoscale defects has proven challenging due to experimental limitations. A combined experimental and first-principles approach has been used to study solute segregation at extended intermetallic phases ranging from 4 to 35 atomic layers in thickness. Chemical mapping by both atom probe tomography and high-resolution scanning transmission electron microscopy demonstrates a markedly different composition for the 4-atomic-layer-thick phase, where segregation has occurred, compared to the approximately 35-atomic-layer-thick bulk phase of the same crystal structure. First-principles predictions of bulk free energies in conjunction with direct atomistic simulations of the intermetallic structure and chemistry demonstrate the breakdown of bulk thermodynamics at nanometer dimensions and highlight the importance of symmetry breaking due to the proximity of interfaces in determining equilibrium properties.
authors.affiliation: Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106-5050, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Titus
authors.affiliation: Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106-5050, USA.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Rhein
authors.affiliation: Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106-5050, USA.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Wells
authors.affiliation: Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106-5050, USA.
authors.forename: Philip C
authors.initials: PC
authors.lastname: Dodge
authors.affiliation: Center for Electron Microscopy and Analysis, The Ohio State University, Columbus, OH 43212, USA.
authors.forename: Gopal Babu
authors.initials: GB
authors.lastname: Viswanathan
authors.affiliation: Center for Electron Microscopy and Analysis, The Ohio State University, Columbus, OH 43212, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Mills
authors.affiliation: Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106-5050, USA.
authors.forename: Anton
authors.initials: A
authors.lastname: Van der Ven
authors.affiliation: Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106-5050, USA.
authors.forename: Tresa M
authors.initials: TM
authors.lastname: Pollock
keywords: Interfaces; Thermodynamics; Transmission electron microscopy; atom probe tomography; cluster expansion; first-principles; metallurgy; solute segregation