Whilst it has long been known that disorder profoundly affects transport properties,recent measurements on a series of solid solution 3d-transition metal alloys reveal two orders of magnitude variations in the residua...Whilst it has long been known that disorder profoundly affects transport properties,recent measurements on a series of solid solution 3d-transition metal alloys reveal two orders of magnitude variations in the residual resistivity.Using ab initio methods,we demonstrate that,while the carrier density of all alloys is as high as in normal metals,the electron mean-free-path can vary from~10Å(strong scattering limit)to~103Å(weak scattering limit).Here,we delineate the underlying electron scattering mechanisms responsible for this disparate behavior.While site-diagonal,spin dependent,potential scattering is always dominant,for alloys containing only Fe,Co,and Ni the majority-spin channel experiences negligible disorder scattering,thereby providing a short circuit,while for Cr/Mn containing alloys both spin channels experience strong disorder scattering due to an electron filling effect.Somewhat surprisingly,other scattering mechanisms-including displacement,or size effect,scattering which has been shown to strongly correlate with such diverse properties as yield strength—are found to be relatively weak in most cases.展开更多
The concept of quasi-particles forms the theoretical basis of our microscopic understanding of emergent phenomena associated with quantum-mechanical many-body interactions.However,the quasi-particle theory in disorder...The concept of quasi-particles forms the theoretical basis of our microscopic understanding of emergent phenomena associated with quantum-mechanical many-body interactions.However,the quasi-particle theory in disordered materials has proven difficult,resulting in the predominance of mean-field solutions.Here,we report first-principles phonon calculations and inelastic X-ray and neutron-scattering measurements on equiatomic alloys(NiCo,NiFe,AgPd,and NiFeCo)with force-constant dominant disorder—confronting a key 50-year-old assumption in the Hamiltonian of all mean-field quasi-particle solutions for off-diagonal disorder.Our results have revealed the presence of a large,and heretofore unrecognized,impact of local chemical environments on the distribution of the species-pair-resolved force-constant disorder that can dominate phonon scattering.This discovery not only identifies a critical analysis issue that has broad implications for other elementary excitations,such as magnons and skyrmions in magnetic alloys,but also provides an important tool for the design of materials with ultralow thermal conductivities.展开更多
基金This work was supported by the Energy Dissipation and Defect Evolution(EDDE),an Energy Frontier Research Center funded by the U.S.Department of Energy(DOE),Office of Science,Basic Energy Sciences under contract number DE-AC05-00OR22725This research used resources of Oak Ridge National Laboratory’s Computer and Data Environment for Science(CADES)and the Oak Ridge Leadership Computing Facility,which is a DOE Office of Science User Facility supported under Contract DE-AC05-00OR22725S.M.acknowledges fruitful discussions with K.D.Belashchenko,B.C.Sales,and K.Jin.S.W.,S.M.,and H.E.would like to thank the DFG(Deutsche Forschungsgemeinschaft)for financial support within the priority program SPP 1538 and the collaborative research centers 689 and 1277.
文摘Whilst it has long been known that disorder profoundly affects transport properties,recent measurements on a series of solid solution 3d-transition metal alloys reveal two orders of magnitude variations in the residual resistivity.Using ab initio methods,we demonstrate that,while the carrier density of all alloys is as high as in normal metals,the electron mean-free-path can vary from~10Å(strong scattering limit)to~103Å(weak scattering limit).Here,we delineate the underlying electron scattering mechanisms responsible for this disparate behavior.While site-diagonal,spin dependent,potential scattering is always dominant,for alloys containing only Fe,Co,and Ni the majority-spin channel experiences negligible disorder scattering,thereby providing a short circuit,while for Cr/Mn containing alloys both spin channels experience strong disorder scattering due to an electron filling effect.Somewhat surprisingly,other scattering mechanisms-including displacement,or size effect,scattering which has been shown to strongly correlate with such diverse properties as yield strength—are found to be relatively weak in most cases.
基金This work was supported as part of the Energy Dissipation and Defect Evolution(EDDE),an Energy Frontier Research Center funded by the U.S.Department of Energy(DOE),Office of Science,and Basic Energy Sciences under contract number DE-AC05-00OR22725This research used resources of the Advanced Photon Source,a DOE Office of Science User Facility operated by Argonne National Laboratory under Contract No.DE-AC02-06CH11357This research used resources of Oak Ridge National Laboratory’s Compute and Data Environment for Sciences(CADES)and the Oak Ridge Leadership Computing Facility,which is a DOE office of Science User Facility supported under Contract DE-AC05-00OR22725.
文摘The concept of quasi-particles forms the theoretical basis of our microscopic understanding of emergent phenomena associated with quantum-mechanical many-body interactions.However,the quasi-particle theory in disordered materials has proven difficult,resulting in the predominance of mean-field solutions.Here,we report first-principles phonon calculations and inelastic X-ray and neutron-scattering measurements on equiatomic alloys(NiCo,NiFe,AgPd,and NiFeCo)with force-constant dominant disorder—confronting a key 50-year-old assumption in the Hamiltonian of all mean-field quasi-particle solutions for off-diagonal disorder.Our results have revealed the presence of a large,and heretofore unrecognized,impact of local chemical environments on the distribution of the species-pair-resolved force-constant disorder that can dominate phonon scattering.This discovery not only identifies a critical analysis issue that has broad implications for other elementary excitations,such as magnons and skyrmions in magnetic alloys,but also provides an important tool for the design of materials with ultralow thermal conductivities.
