While crystal engineering traditionally focuses on the rational design of the perfect periodic lattice, the functional properties of many next generation materials are governed fundamentally by their imperfections. Predicting the energetics of these dilute defects remains a challenge, as the large supercells required to minimize periodic image interactions are often computationally prohibitive. Here we introduce a solid state 'Amons' (Atom-in-Molecule) ansatz that bridges local chemical environments with bulk properties. Drawing on the supramolecular synthon concept where local motifs dictate global packing, we define 'solid state Amons' as a hierarchy of small, tractable periodic fragments that capture the essential local chemistry of the defect.

Using Density Functional Theory with the Exchange hole Dipole Moment (XDM) dispersion model to capture critical non covalent interactions, we analyze the finite size scaling of these fragments. This allows us to accurately extrapolate dilute limit energetics without requiring massive supercells. We validate the approach on substitutional defects and vacancies in h BN and graphene. Our results demonstrate that the defect landscape can be mapped with high fidelity at a fraction of the typical computational cost, providing a scalable tool for the inverse design of defect engineered materials.