Isotropic-compression Bragg-angle shift
= Isotropic-compression Bragg-angle shift
{title2=$d\theta/dp=\kappa\tan\theta/3$}
For an isotropically compressed cubic <crystal>, $d\ln a/dp=-\kappa/3$. Differentiating <Bragg's law> at fixed <wavelength> gives the displayed derivative. Constant <isothermal compressibility> gives $a(p)=a_0e^{-\kappa p/3}$, not an exactly linear lattice parameter. The integrated prediction presumes no intervening structural phase change.