3.Non-stoichiometric compounds Non-stoichiometric compounds are chemical compounds with an elemental composition that cannot be represented by a ratio of well-defined natural numbers,and therefore violate the law of definite proportions.Often,they are solids that contain crystallographic point defects,such as interstitial atoms and vacancies,which result in excess or deficiency of an element, respectively
3. Non-stoichiometric compounds Non-stoichiometric compounds are chemical compounds with an elemental composition that cannot be represented by a ratio of well-defined natural numbers, and therefore violate the law of definite proportions. Often, they are solids that contain crystallographic point defects, such as interstitial atoms and vacancies, which result in excess or deficiency of an element, respectively
10.1.3 non-crystal quasicrystals Quasicrystals are structural forms that are both ordered and nonperiodic.They form patterns that fill all the space but lack translational symmetry. Classical theory of crystals allows only 2,3,4,and 6-fold rotational symmetries,but quasicrystals display symmetry of other orders(folds).They can be said to be in a state intermediate between crystal and glass. Just like crystals,quasicrystals produce modified Bragg diffraction,but where crystals have a simple repeating structure, quasicrystals are more complex
10.1.3 non-crystal quasicrystals Quasicrystals are structural forms that are both ordered and nonperiodic. They form patterns that fill all the space but lack translational symmetry. Classical theory of crystals allows only 2, 3, 4, and 6-fold rotational symmetries, but quasicrystals display symmetry of other orders (folds). They can be said to be in a state intermediate between crystal and glass. Just like crystals, quasicrystals produce modified Bragg diffraction, but where crystals have a simple repeating structure, quasicrystals are more complex
(b quartz crystal quartz glass
quartz crystal quartz glass
10.1.3 Types of Crystals component Physical properties crystal type of the crys inter- action b.P,m.p.rigidity 熔融导 e.g. tal lattice 熔沸点 硬度 电性 ionic ionic Ion bond high hard good NaCl covalant atomic atom bond high hard bad SiO2 atom metalic High hard Cr, metallic ion bond low soft good K,Hg Inter- molecular molecule low soft bad molecular ice force
component Physical properties of the crystal lattice inter- action b.P, m.p. 熔沸点 rigidity 硬度 熔融导 电性 e.g. ionic Ion ionic bond high hard good NaCl atomic atom covalant bond high hard bad metallic atom ion metalic bond High low hard soft good Cr, K, Hg molecular molecule Inter- molecular force low soft bad ice SiO2 10.1.3 Types of Crystals crystal type
§10.2 Metallic Crystals 10.2.1 The Structures of Metallic Crystals 10.2.2 Packing Spheres 10.2.3 Metallic Bond 10.2.4 Metal Alloy 返回
10.2.1 The Structures of Metallic Crystals §10.2 Metallic Crystals 10.2.4 Metal Alloy 10.2.3 Metallic Bond 10.2.2 Packing Spheres