Lattice energy

Model of the calcium sulfide lattice

The lattice energy indicates how much work has to be expended to infinitely far apart the atomic, ionic or molecular components of a solid in a vacuum (i.e. to change into the gas state). The lattice energy is a binding energy . Conversely, its negative is the potential energy when the atoms , molecules or ions come together from an infinite distance to form a crystal lattice , i.e. H. the amount of lattice energy is released when a lattice is formed. ${\displaystyle \Delta _{G}U}$

The lattice energies of ionic compounds such as table salt , metals such as iron and covalently bound polymers such as diamond are, because of the strong, predominantly electrostatic or covalent interactions, considerably greater than with solids such as sugar or iodine , which are made up of neutral molecules and only via van der Waals - Forces interact.

For the calculation of the lattice energy in ionic compounds, see: Madelung constant , Born-Landé equation , Kapustinskii equation .

The lattice energy and the lattice enthalpy differ qualitatively: the lattice energy is an internal energy , while the lattice enthalpy is an enthalpy . The lattice enthalpy also takes into account the volume work to be performed against a constant external pressure. If a molar lattice enthalpy has been determined for the separation of the components of the solid , then the molar lattice energy is: ${\displaystyle p\cdot \Delta V}$ ${\displaystyle \Delta _{G}H}$

${\displaystyle \Delta _{G}U=\Delta _{G}H-p\cdot \Delta V_{m}}$

with the change in volume related to the amount of substance . ${\displaystyle \Delta V_{m}}$

See also

Solvation

Individual evidence

1. ^ Solid State Physics, Neil W. Ashcroft, David N. Mermin, Oldenbourg Verlag, 2007, ISBN 3-486-58273-9 , p. 500, limited preview in Google book search.
2. ↑ Taschenbuch der Chemie, Karl-Heinz Lautenschläger, Werner Schröter, Harri Deutsch Verlag, 2008, ISBN 3-8171-1761-2 , p. 292, limited preview in the Google book search.