Physical Chemistry Chapter vil solid State How do we describe crystalline solids 8 Lattice a lattice is an infinite 1, 2, or 3-d regular arrangement of points, each of which has identical surroundings Any periodic pattern can be described by placing lattice points at equivalent positions within each unit of力 he pattern To recover original pattern we add the motif to each lattice point 20218/21 Chemistry Departme nt of Fudan University 11
Physical ChemistryI Chapter VII Solid State 2021/8/21 Chemistry Department of Fudan University 11 How do we describe crystalline solids ？ — Lattice A lattice is an infinite 1,2, or 3-D regular arrangement of points, each of which has identical surroundings. Any periodic pattern can be described by placing lattice points at equivalent positions within each unit of the pattern. To recover original pattern we add the motif to each lattice point
Physical Chemistry Chapter vil solid State Lattice points must link up-cannot have gaps between adjacent points All lattice points must be identical (with identical environments) Lattice points must show the full symmetry of the structure> next section Patter Motif Lattice 20218/21 Chemistry Departme nt of Fudan University
Physical ChemistryI Chapter VII Solid State 2021/8/21 Chemistry Department of Fudan University 12 ➢ Lattice points must link up - cannot have gaps between adjacent points ➢ All lattice points must be identical (with identical environments) ➢ Lattice points must show the full symmetry of the structure → next section
●a Chapter vil solid State 2D example-Square lattice (sodium chloride NaCl) We define lattice points; these are points with identica/environments 20218/21 Chemistry Departme nt of Fudan University
Physical ChemistryI Chapter VII Solid State 2021/8/21 Chemistry Department of Fudan University 13 2D example – Square lattice (sodium chloride, NaCl) We define lattice points ; these are points with identical environments
Physical Chemistry Chapter vil solid State Choice of origin is arbitrary -lattice points need not be atoms -but unit cell size should always be the same 20218/21 Chemistry Departme nt of Fudan University 14
Physical ChemistryI Chapter VII Solid State 2021/8/21 Chemistry Department of Fudan University 14 Choice of origin is arbitrary - lattice points need not be atoms - but unit cell size should always be the same
●a Chapter vil solid State This is also a unit cell it doesnt matter if you start from na or cl 20218/21 Chemistry Departme nt of Fudan University
Physical ChemistryI Chapter VII Solid State 2021/8/21 Chemistry Department of Fudan University 15 This is also a unit cell - it doesn’t matter if you start from Na or Cl