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Publié par | rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen |
Publié le | 01 janvier 2006 |
Nombre de lectures | 11 |
Langue | English |
Poids de l'ouvrage | 3 Mo |
Extrait
Quantum-Chemical Calculations of
Transition-Metal Oxynitrides
Von der Fakult¨at fu¨r Mathematik, Informatik und Naturwissenschaften der
Rheinisch-Westf¨alischen Technischen Hochschule Aachen zur Erlangung des
akademischen Grades eines Doktors der Naturwissenschaften
genehmigte Dissertation
vorgelegt von
Diplom-Chemiker
Marck-Willem Lumey
aus Heerlen (NL)
Berichter: Universit¨atsprofessor Dr. R. Dronskowski
Universit¨atsprofessor Dr. U. Simon
Tag der mu¨ndlichen Pru¨fung: 30.01.2006
DieseDissertationistaufdenInternetseitenderHochschulbibliothekonlineverfu¨gbarIf one does not fail at times,
then one has not challenged himself.
Ferdinand PorscheParts of this work are already published or submitted for publication:
M.-W. Lumey and R. Dronskowski
The Electronic Structure of Tantalum Oxynitride and the Falsification of
α-TaON
Z. Anorg. Allg. Chem., 629 (2003) 2173
M.-W. Lumey and R. Dronskowski
Quantum-Chemical Studies on the Geometric and Electronic Structures of
Bertholloide Cobalt Oxynitrides
Adv. Funct. Mater., 14 (2004) 371
M.-W. Lumey and R. Dronskowski
First-Principles Electronic Structure, Chemical Bonding, and High-Pressure
Phase Prediction of the Oxynitrides of Vanadium, Niobium and Tantalum
Z. Anorg. Allg. Chem., 631 (2005) 887
T. Bredow, M.-W. Lumey, R. Dronskowski, H. Schilling, J. Pickardt, M. Lerch
Structure and Stability of TaON Polymorphs
Z. Anorg. Allg. Chem., submittedContents
1. Introduction 1
2. Electronic Structure Calculations 3
2.1 Density-Functional Theory . . . . . . . . . . . . . . . . . . . . . 4
2.2 Exchange and Correlation Functionals . . . . . . . . . . . . . . 6
2.3 Applied Density-Functional Methods . . . . . . . . . . . . . . . 7
2.3.1 Pseudopotentials . . . . . . . . . . . . . . . . . . . . . . 7
2.3.2 Augmented Plane Wave (APW) . . . . . . . . . . . . . . 8
2.3.3 Linearized Augmented Plane Wave (LAPW) . . . . . . . 10
2.3.4 Linearized Muffin-Tin Orbital (LMTO) . . . . . . . . . . 11
2.3.5 Bonding analysis: COHP . . . . . . . . . . . . . . . . . . 12
3. Binary Oxides and Nitrides of the First-Row Transition Metals 14
3.1 First-Row Transition-Metal Oxides . . . . . . . . . . . . . . . . 15
3.2 First-Row Transition-Metal Nitrides . . . . . . . . . . . . . . . . 20
4. Oxynitrides of the 3d Transition Metals 25
4.1 3d Transition-Metal Oxynitrides; Structure and Magnetism . . . 26
4.2 Thermodynamic Stability . . . . . . . . . . . . . . . . . . . . . 32
4.3 Supercell Stoichiometry . . . . . . . . . . . . . . . . . . . . . . . 34
5. Oxynitrides of Vanadium, Niobium and Tantalum 39
5.1 Stoichiometrically Precise Vanadium Oxynitride . . . . . . . . . 40
5.2 Niobium Oxynitride. . . . . . . . . . . . . . . . . . . . . . . . . 47
5.3 Tantalum Oxynitride . . . . . . . . . . . . . . . . . . . . . . . . 50
5.3.1 β-TaON . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
iiContents iii
5.3.2 α-TaON . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.3.3 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 62
5.3.4 Mixed Oxynitrides of Niobium and Tantalum . . . . . . 63
5.3.5 High-pressure phases of NbON and TaON . . . . . . . . 65
5.3.6 Anion order in VON, NbON and TaON . . . . . . . . . . 70
6. Summary 73
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
A. Technical Details 84
A.1 LMTO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
A.2 Wien2k . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
A.3 VASP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
A.4 wxDragon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
B. Crystal Data 86
C. Results on VON 87
D. Results on high-pressure phases of TaON 89List of Tables
1 Experimentalpropertiesofthebinarytransition-metaloxidesand
nitrides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2 Calculated energies of the the 3d transition-metal oxides in dif-
ferent spin-orientations . . . . . . . . . . . . . . . . . . . . . . . 16
3 Experimental and calculated band gaps for MnO, FeO, CoO and
NiO in the rocksalt structure. . . . . . . . . . . . . . . . . . . . 17
4 Calculatedandexperimentalformationenthalpiesofthe3dtransition-
metal oxides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5 Calculated energies of the the 3d transition-metal nitrides in dif-
ferent spin-orientations . . . . . . . . . . . . . . . . . . . . . . . 21
6 Calculated energies (eV/f.u.) of the supercell structures with dif-
ferent anion arrangements of the 3d transition-metal oxynitrides. 35
7 Properties of several hypothetical polymorphs of VON . . . . . 41
8 Comparison of the energies and volumes of the educts (V O +2 5
3 VN + N ) and products (5 VON in several different structure2
types) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
9 Experimental and theoretical structure data of NbON on the ba-
sis of pseudopotential-GGA calculations. . . . . . . . . . . . . . 48
10 Theoretical total energies and volumes of NbON as a function of
anionic ordering on the basis of pseudopotential-GGA calculations 49
11 Experimental and theoretical structure data of β-TaON on the
basis of pseudopotential-GGA calculations. . . . . . . . . . . . . 54
ivList of Tables v
12 Theoretical total energies of α-TaON (lattice parameters fixed)
as a function of anionic ordering on the basis of pseudopotential-
GGA calculations. . . . . . . . . . . . . . . . . . . . . . . . . . 57
13 Experimental and theoretically optimized volumes/energies for
α-TaON on the basis of pseudopotential-GGA calculations. . . . 58
14 Energy of the niobium substituted tantalum oxynitrides in com-
parison with the simple ternary compounds, TaON and NbON. 64
15 Properties of several hypothetical polymorphs of TaON. . . . . . 66
16 Theoretical relative energies as a function of anionic ordering for
VON, NbON and TaON. . . . . . . . . . . . . . . . . . . . . . . 70
17 ICOHP values for the N–N, N–O and O–O bonds of VON in the
baddeleyite structures for different anion arrangements. . . . . . 72
18 Experimentalandcalculatedpropertiesof3dtransition-metalni-
trides and oxides. . . . . . . . . . . . . . . . . . . . . . . . . . . 86
19 Properties of all calculated hypothetical polymorphs of VON . . 87
20 Propertiesofallcalculatedhigh-pressurehypotheticalpolymorphs
of TaON.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89List of Figures
1 The partition of a unit cell in localized and interstitial regions . 9
2 Schematic drawing of the APW and LAPW method . . . . . . . 10
3 Differences between the theoretical and experimental formation
enthalpy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4 Experimental and calculated volumes for the 3d transition-metal
nitrides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5 Energy difference between the 3d transition-metal oxynitrides in
the rocksalt and the zinc blende type, for the nonmagnetic case. 26
6 Electronic structure of CrO N in the lowest-energy rocksalt0.5 0.5
type structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7 ElectronicstructureofCrO N inthelowest-energyzincblende0.5 0.5
type structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8 Crystal Orbital Hamilton Populations (COHP) for the Cr–Cr in-
teractions of CrO N in the rocksalt and the zinc blende type 290.5 0.5
9 Energy difference between the 3d transition-metal oxynitrides in
the rocksalt and the zinc blende type. . . . . . . . . . . . . . . . 31
10 Formation energy of the 3d transition-metal oxynitrides relative
to the binary oxides and nitrides. . . . . . . . . . . . . . . . . . 33
11 Supercell containing 2×2×2 conventional cubic cells of the zinc
blende structure of CoO N . . . . . . . . . . . . . . . . . . . 350.5 0.5
12 Radial distribution function(RDF)of theCo–Nand Co–Ointer-
atomic distances in the CoO N . . . . . . . . . . . . . . . . . 360.5 0.5
13 TheoreticalΔE-xdiagramcalculatedforvariousCoO N com-x 1−x
positions according to Equation 1. . . . . . . . . . . . . . . . . . 37
vi