Bài tập về nhà môn Vật lý chất rắn - Số 2 (Có đáp án)

hcp and fcc Structures

α-Co has an hcp structure with lattice spacings of a = 2.51 Å and с = 4.07 Å; β-Co is fcc, with a cubic lattice spacing of 3.55 Å. What is the difference in density between the two forms?

Neutron Diffraction Device

A collimated beam of neutrons of all energies is incident on a powder of cubic, monoatomic crystallites. What will happen to the neutron beam and what will the energies of the colimated neutrons exiting the powder be? How can this be used experimentally?

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  1. 1. hcp and fcc Structures α-Co has an hcp structure with lattice spacings of a = 2.51 Å and с = 4.07 Å; β-Co is fcc, with a cubic lattice spacing of 3.55 Å. What is the difference in density between the two forms? 2. Neutron Diffraction Device A collimated beam of neutrons of all energies is incident on a powder of cubic, monoatomic crystallites. What will happen to the neutron beam and what will the energies of the colimated neutrons exiting the powder be? How can this be used experimentally? 3. Powder Diffraction of hcp and fcc Crystals Cobalt has two forms: α -Co, with hcp structure (lattice spacing of a = 2.51 Å) and β -Co, with fcc structure (lattice spacing of аcubic = 3.55 Å). Assume that the hcp structure has an ideal c/a ratio. Calculate and compare the position of the first five X-ray powder 4 diffraction peaks. The quantity 퐾 = 휆푠푖푛휃 can be used to characterize the peak positions (here λ is the wavelength of the X-ray radiation and 2θ is the scattering angle).