Magnetoelastic coupling and effects of uniaxial strain in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>α</mml:mi><mml:mo>−</mml:mo><mml:msub><mml:mi mathvariant="normal">RuCl</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math> from first principles

We present first-principles results on the magnetoelastic coupling in $\alpha$-RuCl$_3$ and uncover a striking dependence of magnetic constants strain effects. Different interactions are found to respond very unequally variations lattice, with Kitaev interaction being most sensitive. Exact diagonalization our model reproduce recent measurements structural Gr\"uneisen parameter explain origin negative magnetostriction $\alpha$-RuCl$_3$, disentangling contributions related different anisotropic g factors. Uniaxial perpendicular honeycomb planes is predicted reorganize relative strengths, strongly enhancing while simultaneously weakening other exchanges under compression. may therefore pose fruitful route experimentally tune nearer limit.