# Born–Mayer equation

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.[1]

${\displaystyle E=-{\frac {N_{A}Mz^{+}z^{-}e^{2}}{4\pi \epsilon _{0}r_{0}}}\left(1-{\frac {\rho }{r_{0}}}\right)}$

where:

• ${\displaystyle \rho }$ = a constant dependant on the compressibility of the crystal; 30 pm works well for all alkali metal halides