生物化工基礎(chǔ)

1、STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/071 Magnetic particles for recording applications 3d/4d et 3d/5d Alloys Stability: High magnetic anisotropy 4d,5d element Example: CoxRh1-x nan

2、oparticles Sensitivity:High magnetic moments per atom 3d elements High density:Small size nanoparticles STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/072 q Cobalt : hcp (T750K) q Rhodium :

3、fcc fcchcp q Alloy: hcp (x50,5%) Disordered solid solution W. Koster, Z. Metallkunde, 43 (1952) Bulk crystals: Co, Rh and Co1-xRhx STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/073 (fcc) Oc

4、tahedron: 1st and 2d neighbours distances )d2,d( mmmm ABCABC (111) stacking AB C A Tetrahedron: 1st neighbours distance )d( mm Close packed structures : face centered cubic (fcc) and hexagonal compact (hcp) STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar

5、 at Research Center of Laser Fusion, Mian Yang, China April 2-6/074 (fcc) Close packed structures : face centered cubic (fcc) and hexagonal compact (hcp) In between two successive (111) planes (AB) or (BC) or (CA) Exist also in the other closed packed hcp structure (ABAB.) Tetrahedron and octahedron

6、 are the building blocks of close-packed structures 1st and 2d neighbours distances are characteristic of close-packed structures Tetrahedron: 1st neighbours distance )d( mm Octahedron: 1st and 2d neighbours distances )d2,d( mmmm STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORI

7、LLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/075 Close-packed nanoparticles Based on tetrahedrons only non periodic-based polytetrahedrons the 2d neighbours distance is absent)d2( mm mm d Based on tetrahedrons and octahedrons mm d2 mm d 1st and 2d neighbours

8、 distances are present mm d periodic or non periodic-based nanoparticles STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/076 qINTRODUCTION qEXPERIMENTAL RESULTS qMODELLING STRUCTURE, CHEMICAL

9、 ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/077 Chemical techniques in mild conditions (T=300 - 400K) Co-decomposition by H2 of the two organometallic precursors in THF Size and dispersion stabilized by pol

10、ymer (PVP), or ligand (HDA) Pure Co, M, Co3M1 Co1M1, Co1M3 (close packed metals and alloys in cristalline state) Synthesis Experiments Structure TEM, HREM Wide angle x-ray scattering Chemical distribution EFTEM EXAFS PVP- Co1Rh1 mean f f = 1.8 nm STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANO

11、PARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/078 CoRh Co Co3Rh1 Co1Rh1 Co1Rh3 Rh r (nm) a. u. PVP hcp fcc WAXS measurements of radial distribution function dmm CoRu r (nm) a. u. PVP hcp hcp STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NA

12、NOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/079 Co Rh Pt Ru 3d 4d 5d 678 Specific non periodic Structures associated to Co and Co rich particles Pt Co fcc hcp a. u. CoPt Pt1Co3 Pt1Co1 Pt3Co1 Pt5Co1 a. u. Pt Ru PtRu fcc hcp Pt1Ru9 Pt1Ru5 P

13、t1Ru3 Pt1Ru1 Pt3Ru1 STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0710 First neighbour distance dmm as deduced from WAXS measurements of radial distribution function Bulk fcc Rh concentrati

14、on (at. %) nanoparticles bulk fcc hcp CoRh Ru concentration (at. %) CoRu STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0711 HREM image showing a four fold symetry in the Co nanoparticle STR

15、UCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0712 Elemental map : cobalt rhodiumZero loss image - Co3Rh1 dmm higher than in the bulk (shifted towards dmm in pure Rh) Rh-rich core ? EXAFS : ox

16、idation at cobalt edge, Rh environment for Rh EFTEM : on bigger particles (5- 6 nm) synthesized in HDA (hcp-fcc) STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0713 Co concentration (at. %)

17、nanoparticles bulk (B/at) (B/at) Co concentration (at. %) nanoparticles bulk + CoRhCoRu Magnetic moment measurements STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0714 qWhich structure? qWh

18、ich chemical order? qCan they explain the magnetic moment enhancement? STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0715 qINTRODUCTION qEXPERIMENTAL RESULTS qMODELLING STRUCTURE, CHEMICAL

19、ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0716 Introduction Levels of materials modelling 10102103104105106 force-field number of atoms accuracy tight-binding ab initio (parameter-free) quantum chemistry H

20、artree-Fock, configuration interaction density functional theory empirical potentials molecular dynamics Monte-Carlo Compromise between accuracy and computational tractability our study STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center o

21、f Laser Fusion, Mian Yang, China April 2-6/0717 ab initio DFT vStudy bonding mechanisms at the local level vInfer general tendencies as a function of the chemical and structural order small clusters large clusters surfaces now Introduction semi-empirical methods vModel larger particles vStudy proper

22、ties that are not easily calculated in ab initio (CPU time) bulks STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0718 ab-initio Density Functional Theory calculations Use of VASP code DFT-GG

23、A (PW91) calculations : spin only, colinear magnetism PAW method (Projector Augmented Wave) advantages : very good accuracy, espec. for magnetic systems reasonable computation time Calculation of ground state properties: cohesive energy Ecoh = E(system) - E(isolated atoms) (eV/at.) geometry local /

24、average magnetic moments (B/at.) Tests on bulks and small clusters of pure materials: OK Tests of different XC functionals STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0719 4*3 parameters:

25、 , ij = CoCo, RhRh, CoRh rij0 : normalisation factors (first neighbours distances) ) r r (p j ij j ) r r (q iji ij ij ij ij ij ij eAeE 112 2 00 2 1 q N-body central force field model : v second-moment approximation of the tight-binding model: d-electron band contribution (n-body) v Born-Mayer short

26、distance electron core-core repulsion (pair interaction) ij ij qpA ijij , Semi-empirical calculations STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0720 q Parameters fit: v Co-Co and Rh-Rh

27、direct interactions from F. Cleri, V. Rosato, (Phys. Rev. B, 48 (1993): Cohesive energy: Ec Elastic constants: Cij, Lattice parameter(s): a (c). v Co-Rh mixed interactions: Cohesive energies Lattice parameters hypothetical ordered alloys at the studied compositions of ab-initio Semi-empirical calcul

28、ations STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0721 qWhich structure? qWhich chemical order? qCan they explain the magnetic moment enhancement? STRUCTURE, CHEMICAL ORDER AND MAGNETISM

29、 OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0722 Which structure for the pure Co particles? Polytetrahedral 100 150 at. Apparent four fold symetry axis Reproducing the WAXS curves STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/

30、4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0723 Polytetrahedral geometrical models 105 atoms Van de Waal, Non Cris. Sol. 189 Exp Model 024681012 r (A) 137 atoms Corresponding HREM simulations Doy et al, Cond. Mat. 97 024681012 r (A)

31、 Exp Model View along the 4 fold symetry axis STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0724 Co particles (100N150) -3.9 -3.85 -3.8 -3.75 -3.7 -3.65 90100110120130140150160 Number of at

32、oms T = 0 K Potential energy Ep (eV/at.) MD Study Thermalisation in the liquid state 1,2000,000 DM steps run Snapshots every 10,000 steps Quenching to T = 0 K Selection of the lowest energy configurations STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar a

33、t Research Center of Laser Fusion, Mian Yang, China April 2-6/0725 -3.78 -3.76 -3.74 -3.72 -3.7 -3.68 0200400600800100012001400 Cohesive energy at 0 K (eV/at.) Recovery and quenching (K) 0 0.2 0.4 0.6 0.8 1 024681012 300 K 1200 K a. u. d () 300K1200 K Co particle (105 at.) 60-70 meV Radial distribut

34、ion function STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0726 RELATIVE STABILITIES OF THE DIFFERENT Co MODELS Perfect octahedron 50-60 meV 30 meV -3.86 -3.84 -3.82 -3.8 -3.78 -3.76 -3.74

35、-3.72 -3.7 020040060080010001200 Ep (T=0K) T (recovery and quenching) 105 polytetrahedron 137 polytetrahedron 129 octahedron 137 octahedron 105 octahedron 147 (surface vacancy + top surface atom) Perfect polytetrahedral structures are unstable relative to the defective octahedral structures Most pro

36、bable: Metastable glass like high temperature disordered polyhedral structures STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0727 024681012 r (A) a. u. Exp 105 at. 129 at. 137 at. High T 10

37、5 at. 137 at. Polytetrahedra STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0728 qWhich structure? qWhich chemical order? qCan they explain the magnetic moment enhancement? STRUCTURE, CHEMIC

38、AL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0729 Which chemical order for the CoxRh1-x particles ? Co rich: Polytetrahedral Rh rich: with octahedral sites 100 500 at. Strong non linear dmm dilation with x

39、 Reproducing the WAXS curves Monte Carlo Metropolis study: Simulated Annealing with Atomic Relaxation and Exchanges between Co and Rh atoms. A large variety of initial states: Disordered, Ordered, Core/Shell fcc, hcp, Cuboctahedral, Different initial temperatures STRUCTURE, CHEMICAL ORDER AND MAGNET

40、ISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0730 Co3Rh1(hcp) Co Rh distance to centre () Co1Rh1(fcc)Co1Rh3(fcc) 300K MCM Relaxation and Exchange Structure and chemical order STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d

41、NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0731 Co1Rh1Co1Rh3 Co Rh distance to centre () Co3Rh1 1600K TO 300 K MCM Relaxation and Exchange Simulated Annealing Structure and chemical order STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4

42、d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0732 Radial Distribution Functions Experimental Model 1600 K Simulated annealing 300K Structure and chemical order STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO,

43、CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0733 Intermetallic distance dmm(nm) Structure and chemical order 0.25 0.26 0.27 00.51 d0 (nm) at % Rh simulations experimental Bulk : fcc model fcc exp. hcp exp. STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPAR

44、TICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0734 Conclusion on structure and chemical order q Co rich particles : Co, Co3Rh1, CO1Rh1 v Structure Metastable Disordered glass like polytetrahedral structure vChemical order Equilibrium distributio

45、n Rh core Co surface segregation structure Small Co core q Rh rich particles : Rh, Co1Rh3 vStructure Stable fcc ordered vChemical order Rh core Co surface segregation structure Possible very small Co core STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar a

46、t Research Center of Laser Fusion, Mian Yang, China April 2-6/0735 qWhich structure? qWhich chemical order? qCan they explain the magnetic moment enhancement? STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang,

47、China April 2-6/0736 magnetism magnetism enhanced by geometrical dilation interatomic distance magnetism enhanced by coordination reduction coordination Geometrical contraction at reduced coordination z = 2z = 6z = 12 Magnetism: from the single atom to the infinite cristal Ecoh Magnetic moment (B) M

48、onolayer (111) Linear chain bulk cfc Isolated atom z = 12 z = 2 z = 6 Cobalt example STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0737 31.571.93Co Co From the atoms up to the bulks 31.82 R

49、h Rh 0.00 Magnetic moment per atom (B/atom) CoRh Co Rh xCo = 0.5 2.29 1.60 1.430.40 Magnetism: alloying effect STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0738 Fcc(111) Rh surface doped w

50、ith Co vacuum towards bulk S position S-1 position S-2 position -0,60 -0,55 -0,50 -0,45 -0,40 -0,35 -0,30 -0,25 -0,20 0,000,250,500,751,00 S S-1 S-2 single layer Co concentration Formation energy (eV) subsurface position favored Magnetism: surface effect Co surface segregation? STRUCTURE, CHEMICAL O

51、RDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0739 Fcc(111) Rh surface with Co monolayer vacuum towards bulk Co surface segregation? There is a surface Co segregation With a marked preference for the subsurface

52、 position S position S-1 position S-2 position -2,10 -2,00 -1,90 -1,80 -1,70 -1,60 -1,50 -1,40 1234567 position of the Co ML magnetic non-magnetic Adsorption energy (eV/Co at) Magnetism: surface effect STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at R

53、esearch Center of Laser Fusion, Mian Yang, China April 2-6/0740 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 0.000.200.400.600.801.00 concentration en Co intracouche moment magntique (B/atome) Moment magntique de Co Co subsurface Co preserves a high magnetic moment 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50

54、 0.000.200.400.600.801.00 concentration en Co intracouche moment magntique (B/atome) Co subsurface Subsurface position stable an highly favorable for magnetism: effective giant magnetic moments there are high induced moments on neibourghing Rhs Effective magnetic moment (Co+ induced Rh) Co subsurfac

55、e vacuum Magnetic enhancement at surface? Magnetism: surface effect STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0741 importance of size effects RhCo rat =1.25 1.35 1.39 Pt Atomic radius C

56、o Core ? ConRh13-n centred icosahedral clusters dradial dsurface Icosahedral specific geometry : radial bonds in compression surface bonds in tension Magnetism: size effect STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusio

57、n, Mian Yang, China April 2-6/0742 Ecoh (eV/at) Sz (B) RhCo legend 3,34 31 3,79 21 Co Core and magnetic enhancement? Magnetism: size effect 3,87 15 3,44 21 3,30 21 3,78 21 STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion

58、, Mian Yang, China April 2-6/0743 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 0.000.250.500.751.00 Co concentration average magnetic moment (B/atom) N=2N=3 N=4N=5 N=6N=7 N=13bulks atoms isolated atoms dimers bulks N= 4 4 N= 6 4 N= 5 4 N= 3 4 N= 7 N=13 4 Strong enhancement in nanoparticles compared to bu

59、lk CoMRhN Mean magnetic moment Comparaison CoMRhN et CoMPtN Magnetism: size effect STRUCTURE, CHEMICAL ORDER AND MAGNETISM OF 3d/4d NANOPARTICLES J. MORILLO, CEMES/CNRS Seminar at Research Center of Laser Fusion, Mian Yang, China April 2-6/0744 Rh37Co Sz = 18 B = 0.47 B/atom Remarquable magnetic enh

60、ancement : eff(Co)=16 B but antiparallel moments at the surface Vers des particules de taille exprimentale Rh38 Sz = 2 B = 0.05 B/atom (exp. : 0.160.13 B/atom for Rh34) Magnetic core poorly magnetic Local magnetic moments chart (B)Local magnetic moments chart (B) Rh38 et Rh37Co Nanoparticles Magneti