Consider a free electron, empty lattice model with effective mass m* in a simple cubic crystal...
Consider the free electron energy bands of an fcc crystal lattice in the empty lattice approximation in the reduced zone scheme in which all k’s are in the first Brillouin zone. Plot in the [111] direction the energies of all bands up to 6 times the lowest band energy at the zone boundary at = (2?/a)( 1/2 , 1/2 , 1/2 ). Let this be the unit of energy. This problem shows why band edges need not be necessarily at...
(b) A caesium-bromide crystal has a simple cubic lattice with lattice constant a= 4.30 A. The basis of the crystal contains one caesium atom at fi = (0,0,0) and one bromine atom at r2 = (a/2, 2/2,a/2), where the vectors and are expressed with respect to the Cartesian basis vectors i, j, k. (i) The relative atomic mass of Cs is 133 amu and the relative atomic mass of Br is 80.0 amu, where I amu = 1.66 x 10-2...
Bottom pictures are 7.7 for context 7.4 Repeat the calculation of Section 7.7 for the empty lattice but for the foc case and the [111] direction. 7.7 The Empty Lattice and Simple Metals We again use our imaginary powers to control the strength of the potential. We assume a finite potential to define the lattice and then decrease it to an insignificantly low value so that the electrons become free. This is the empty lattice: it is a 'ghost' lattice,...