x1,x2,a1,a2分别指两种单质的百分含量和点阵常数.

一般写成:a=x1a1+(1-x1)a2

因为X1+X2=1,有时把X写成C

In metallurgy, Vegard's law is an approximate empirical rule which holds that a linear relation exists, at constant temperature, between thecrystal latticeparameter of analloyand the concentrations of the constituent elements.

For example, consider the semiconductor compound InPxAs1-x. A relation exists between the constituent elements and their associated lattice parameters, a, such that:

aInPAs = xaInP + (1 − x)aInAs

One can also extend this relation to determine semiconductor band gap energies. Using InPxAs1-x as before one can find an expression that relates the band gap energies, Eg, to the ratio of the constituents and a bowing parameter b: