The Born-Oppenheimer approximation provides a description of heavy-quark mesons firmly based on lattice QCD, but its validity is limited to the lightest states lying far below the first open-flavour meson-meson threshold. This limitation can be overcome in the diabatic framework, a formalism first introduced in molecular physics, where the dynamics is encoded in a potential matrix whose elements can be derived from unquenched lattice QCD studies of string breaking. The nondiagonal elements of the potential matrix provide interaction between heavy quark-antiquark and meson-meson pairs, from which the mixing of quarkonium states with molecular components and the OZI-allowed strong decay widths are directly calculated. This allows for a QCD-based unified description of conventional quarkonium and unconventional mesons containing quark-antiquark and meson-meson components, what has proved to be successful for charmoniumlike [1, 2] and bottomoniumlike  resonances.
 R. Bruschini and P. González, Diabatic description of charmoniumlike mesons, Phys. Rev. D 102, 074002 (2020).
 R. Bruschini and P. González, Diabatic description of charmoniumlike mesons II: mass corrections and strong decay widths, Phys. Rev. D 103, 074009 (2021).
 R. Bruschini and P. González, Diabatic description of bottomoniumlike mesons, arXiv:2105.04401 [hep-ph] (2021).