513.001 Molecular and Solid State Physics

Return to
problem list

Wolfram Alpha

Physical
Constants

Periodic System
of Elements

      

Compressibility of NaCl

The cohesive energy of a NaCl crystal can be described by the equation

The material parameters for NaCl are ρ = 0.321 Å, zλ = 1.05×10-8 erg, and α = 1.748. Here R is the distance between nearest neighbors. Calculate the bulk modulus B = -V(dp/dV) and the compressibility κ = 1/B of an ideal sodium chloride crystal at T = 0 K. Here V is the volume and p is the pressure. The lattice constant of NaCl is 0.564 nm.

At T = 0 K, the entropy is zero so the total cohesive energy is Utot = -p dV. This means that the bulk modulus at low temperature is,

.

1 erg = 10-7 J.