The Born–Mayer equation is an equation that is used to calculate the lattice energy of a crystalline ionic compound. It is a refinement of the Born–Landé equation by using an improved repulsion term.
E
=
−
N
A
M
z
+
z
−
e
2
4
π
ϵ
0
r
0
(
1
−
ρ
r
0
)
where:
NA = Avogadro constant;
M = Madelung constant, relating to the geometry of the crystal;
z+ = charge number of cation
z− = charge number of anion
e = elementary charge, 1.6022×10−19 C
ε0 = permittivity of free space
4πε0 = 1.112×10−10 C2/(J·m)
r0 = distance to closest ion
p = a constant dependant on the compressibility of the crystal; 30 pm works well for all alkali metal halides
