Past exam of the chemistry course of the year 4 of the natural sciences course of the University of Cambridge / 2022 / Paper 3 / Section D / 43 / b / v

At fixed number density, attempt frequency, nearest-neighbour distance and barrier, the conductivities have ratio ${\sigma }_{\mathrm{sc}}:{\sigma }_{\mathrm{bcc}}:{\sigma }_{\mathrm{fcc}}=1:4/3:2$. Thus the face-centred cubic array is largest. Numerically,The small value is consistent with the low supplied carrier number density and strongly activated hopping. This comparison holds $n$ fixed rather than comparing fully occupied crystal structures, whose site densities at the same neighbour distance differ.