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Advanced Inorganic Chemistry

Advanced Inorganic Chemistry
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Dr.LeonBurns,New Zealand,Researcher
Published Date:21-07-2017
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Advanced Inorganic Chemistry (Part 1) Basic Solid State Chemistry WS 05/06 (H.J. Deiseroth)Topics of the complete lecture Topics of the complete lecture • Introduction – special aspects of the solid state • Structure of solids • Basic crystallography • Characterization of solids: diffraction techniques, electron microscopy, spectroscopy, thermal analysis • Bonding in solids • Real structure of crystals, defects • Electrical, magnetic and optical properties • Synthesis of solids • Structure-property relationsResources ResourcesResources Resources Textbooks: Shriver, Atkins, Inorganic Chemistry (3rd ed, 1999) W.H. Freeman and Company (Chapter 2, 18 ...) recommendation german very good, but not basic level Internet resources • (german) • (pdf-downloads) • IUCR-teaching resources (International Union for Crystallography, advanced level)Resources Resources JournalsOutline – 15.10.04 Outline – 15.10.04 1. Introduction 2. Structure of solids 2.1 Basics of structures 2.2 Simple close packed structures: metals 2.3 Basic structure types (structure of simple salts) 2.4 More complex structures Oxides... 2.5 Complex structures 2.6 Structure of nanomaterials1. Introduction1.Introduction Why is the solid state interesting? Most elements are solid at room temperature1. Introduction Special aspects of solid state chemistry • Close relationship to solid state physics • Importance of structural chemistry • knowledge of several structure types • understanding of structures • Physical methods for the characterization of solids • X-ray structure analysis, electron microscopy… • thermal analysis, spectroscopy, conductivity measurements ... • Investigation and tuning of physical properties • magnetism, conductivity, sorption, luminescence • defects in solids: point defects, dislocations, grain boundaries • Synthesis • HT-synthesis, hydrothermal synthesis, soft chemistry • strategies for crystal growth (physics)1. Introduction Classifications for solids (examples) • Degree of order • long range order: crystals (3D periodicity) • long range order with extended defects (dislocations…) • crystals with disorder of a partial structure (ionic conductors) • amorphous solids, glasses (short range order) • Chemical bonding – typical properties • covalent solids (e.g. diamond, boron nitride): extreme hardness ... • ionic solids (e.g. NaCl): ionic conductivity ... • metals (e.g. Cu): high conductivity at low temperatures • conductivity: metals, semiconductors, insulators, superconductors… • magnetism: ferromagnetism, paramagnetism… • Structure and Symmetry • packing of atoms: close packed structure (high space filling) • characteristic symmetry elements: cubic, hexagonal…2. Basic Structures2.1 Basics of Structures Visualization of structures Example: Cristobalite (SiO ) 2 Description of packing Description of environment Description of topology Bragg jun. (1920) Sphere packing Pauling (1928) Polyhedra Wells (1954) 3D nets2.1 Basics of Structures Approximation: atoms can be treated like spheres Concepts for the radius of the spheres elements or element or compounds compounds compounds only („alloys“) = = = d/2 of single bond d – r(F, O…) d/2 in metal in molecule problem: reference2.1 Basics of Structures Trends of the atomic radius • atomic radii increase on going down a group. • atomic radii decrease across a period • particularities: Ga Al (d-block) (atomic number)2.1 Basics of Structures Trends of the ionic radii • ionic radii increase on going down a group cf. atomic radii • radii of equal charge ions decrease across a period • ionic radii increase with increasing coordination number (the higher its CN the bigger the ions seems to be ) • the ionic radius of a given atom decreases 2+ 3+ with increasing charge (r(Fe ) r(Fe )) • cations are usually the smaller ions in a cation/anion combination + - (exception: r(Cs ) r(F ))2.1 Basics of Structures Determination of the ionic radius Structure analyses, most important method: Ionic radius = d – r(F, O…) X-ray diffraction L. Pauling: 2- • Radius of one ion is fixed to a reasonable value (r(O ) = 140 pm) • That value is used to compile a set of self consistent values for other ions.2.1 Basics of Structures Structure and lattice – what is the difference? Example: structure and lattice in 2D • Lattice • pattern of points • no chemical information, mathematical description • no atoms, but points and lattice vectors (a, b, c, , , ), unit cell • Motif (characteristic structural feature, atom, group of atoms…) • Structure = Lattice + Motif • contains chemical information (e. g. environment, bond length…) • describes the arrangement of atoms2.1 Basics of Structures Unit cell Unit Cell (interconnection of lattice and structure) • an parallel sided region of the lattice from which the entire crystal can be constructed by purely translational displacements • contents of unit cell represents chemical composition (multiples of chemical formula) • primitive cell: simplest cell, contain one lattice point2.1 Basics of Structures Unit cell – which one is correct? Conventions: 1. Cell edges should, whenever possible, coincide with symmetry axes or reflection planes 2. The smallest possible cell (the reduced cell) which fulfills 1 should be chosen2.1 Basics of Structures Unit cells and crystal system • millions of structures but 7 crystal systems • crystal system = particular restriction concerning the unit cell • crystal system = unit cell with characteristic symmetry elements (later) Crystal system Restrictions axes Restrictions angles Triclinic - -  ° Monoclinic -  ° Orthorhombic -  ° Tetragonal a = b  ° ° Trigonal a = b  ° ° Hexagonal a = b  ° Cubic a = b = c