sem1 Flashcards

Question

What causes efficency of scattering to decrease rapidly

Answer 1

as 2theta increases

Answer 2

Measure of how effciently an atom scatters Xrays under specific conditions

Answer 3

A large scattering amplitude is obtained only when the contributions from all the lattice points are in phase, and this is achieved when, K.a = 2πh, K.b = 2πk, K.c = 2πl

Answer 4

dhkl =2π/|Ghkl|

Answer 5

-Plot recipocal lattice of crystal -Draw wavevectors of incident beam k which terminated at reciprocal lattice point -Draw sohere of radius k=2pi/lamda Diffracted beam will be formed if Ewald sphere intercepts any point in the reciprocal lattice The Ewald sphere is a sphere of the radius defined as the reciprocal of the wavelength of the incident wave 1/λ,

Answer 6

mathematical space which corresponds to FT of real space

Answer 7

region closest to center of recipocal space which contains all possible wavevectors which can be diffracted by crystal lattice

Answer 8

momentum of wave, e.g xrays or electrons if waves diffracted

Answer 9

a∗ =2π/a,i b∗ =2π/a,j c∗ =2π/a,k

Answer 10

a∗ = (2π/a)(j + k), b∗ = (2π/a)(i + k), c∗ = (2π/a)(i + j)

Answer 11

a = (1/2)a(j + k), b = (1/2)a(i + k), c = (1/2)a(i + j)

Answer 12

h+k+l must be even

Answer 13

h, k and l must be either all odd or all even

Answer 14

Particle in the box problem −((hbar^2)/2m)(∇^2)ψ = epsilonψ epsilon = energies of electrons

Answer 15

g(epsilon) = [V/(2(π^2)(hbar^3))]((2m)^3/2)(Epsilon^1/2)

Answer 16

Highest energy state occupied by electron at absolute zero temperature

Answer 17

f(ε,T)=1/ exp((ε-εf)/kbt))+1

Answer 18

n = density of states x occupation of states at temp g(ε) x f(ε,T)

Answer 19

No electrons satisfy diffraction conditions

Answer 20

j = nqv = [(n tau e^2)/m(e)] = sigma E

Answer 21

sigma = [(n tau e^2)/m(e)] =n e mew

Answer 22

Lattice Vibrations

Answer 23

Resistivity = temperature-independent resistivity (ideal resistivity) and its temperature-dependent resistivity (residual resistivity).

Answer 24

The implication of Matthiessen's rule is that two different samples of the same metal, one pure (with minimal defects) and the other impure or alloyed, should exhibit similar resistivity vs temperature curves. However, the impure sample will have a higher overall resistivity due to the presence of additional defects, leading to an offset in the curves corresponding to the residual resistivity.

Answer 25

EH = RHB × j

Answer 26

Why causes materials behavoiur when conductinf electricity 1- Peroidocity and Bloch Equations 2- Free Electrons and not so free electrons 3- Brillouin Zones 4- Occupying energy bands -

Answer 27

Periodic potential of ion cores as weak perturbation on band electrons Energy Gaps and the Bragg Condition Standing Waves and Energy Gaps Band Structure Calculation:

Answer 28

The opposite approach to the nearly free electron model, the tight binding approximation considers the electrons to be tightly bound to the atoms that make up the crystal. When the atoms are widely separated the wavefunctions of the valence electrons will be those of the isolated atoms. As the distance between them decreases we might expect that the electrons will begin to move from one atom to the next. We can consider this motion as the transfer of an electron from one state on the atom to the same state on a neighbouring atom. 1- find suitable wavefunction 2- Calculate E(k) 3- Consider tight binding in sc lattice

sem1 Flashcards

(55 cards)