Amisha Asked a Question
December 25, 2020 1:25 pmpts 30 pts
here p is Number of atoms per ui Find accoustical & optical branches in following solids Graphite2 &C) NE (in) Diamond 3 () Graphene 2) N 2 In diatomic there are two atoms basic thus p 2 (ii) Sol. () 8otems pPerwt ul in diomendl Total branches = 3p 3 x 2 6 So, (3 accoustical + 3 optical) Graphite is 2D structure with 4 atomsin primitive unit cell. (i) Total branches p 4 So, (6 optical + 2 accoustical) (ii) Graphene is 2D structure with 2 atom basis thus total branches = 2 x 2 =4 (2 accoustical + 2 optical) A linear diatomic lattice of lattice constant a with masses M as m, (M> m) are coupled E constant C. The dispersion relation is given by Q. (GATE o=CM+m Mm 1/2 M+m 4C Kka leradnda Mm Mm 2 Which one of the following statement is incorrect? (A) The atoms vibrating in transverse mode correspond to the optical branch. (B) The maximum frequency of the acoustic branch depends on the mass of the lig. m. (C)The dispersion of frequency in the optical branch is smaller than in the acousi (D) No normal modes exist in the acoustic branch for anv frequency greater than tne frequency at k = a Contact Us: Wehsite 10
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  • Indrajeet maurya thankyou
    see the attachment
    • cropped4526851100702235932.jpg
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  • Amisha
    and in second question option be should also be wrong
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  • Amisha
    there are 8 atoms in the unit cell of diamond so total branches should be 24 in first question
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