Hcp structure . Show that the c/a ratio for an ideal hexagonal close- packed  structure is  (8/3)^1/2 = 1.633 . if c/a is significantly  larger than this value , the crystal structure may be thought  of as composed  of planes of closely packed atoms, the planes being loosely stacked.

p9C.1 Familiarity with the magnitudes of overlap integrals is useful when con- sidering bonding abilities of atoms, and hydrogenic orbitals give an indication of their values. (a) The overlap integral between two hydrogenic 2s orbitals is 1 ( ZR ZR +. 2а, " 12 а, 1 + ZR 240 a, -ZR/Z0 S(2s, 2s)={1+ Plot this expression. (b) For what internuclear distance is S(2s,2s) = 0.50? (c) The side-by-side overlap of two 2p orbitals of atoms of atomic number Z is ZR 1 ( ZR ZR S(2p,2p) ={1+ 10 a, 2a, 120 a. Plot this expression. (d) Evaluate S(2s,2p) at the internuclear distance you calculated in part (b).

The function F(E) shown here is 10 E-Ho 0 KT -10 0.5 → F(E) a. the Fermi function, fo(E) Ob. 1 - fo(E) Oc. 1 + fo(E) Od. kT Ofo/OE Oe.- KTOfo/OE