Payal posted an Question
October 15, 2021 • 21:50 pm 30 points
  • CSIR NET
  • Physical Sciences

Ex. find accoustical & optical branches in following solids ) diamond (ii) graphite (ii) graphene

Ex. Find accoustical & optical branches in following solids ) Diamond (ii) Graphite (ii) Graphene

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  • Payal

    And if so then why we take p=4 in graphite inspite of being having 2 atom basis

  • Payal

    If graphite and graphene both are two atom basis with 2 D structure ,then their no. of branches should be same

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    Graphite is a 2D structure having atomic basis 4 ... four carbon atoms are bonded in a basis whereas in graphene atoms basis is 2

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    Thanks

  • Payal

    but in diamond no. of atoms per unit permittive cell are 8 and in graphene these are 6 as u write that in graphite we have 4 atoms per unit permittive cell

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    Yes you are right no of primitive cells is 8 but here we check the no. of atoms in basis so Diamond is a 3D crystal structure with a face centered cubic Bravais lattice and "two atoms in the basis". We used this value as p and similar for graphite and graphene it is a 2D structure with no. of atomic basis 2.

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