Typically not on their own - it's very easy to calculate an optimized structure that is incorrect, so you typically want some sort of justification for your str

Typically not on their own - it's very easy to calculate an optimized structure that is incorrect, so you typically want some sort of justification for your structure. Typically you would be calculating one of these geometries along the way to calculating other interesting properties to either compare with experiment or make new predictions (or both). The "gold standard" is... comparison with a crystal structure from X-ray diffraction. In my field (small inorganic molecules used as catalysts), I typically calculated the structure along the way to calculating the molecular orbitals for describing the electronic structure (important for understanding many properties of the catalyst and its reactivity) and predicting the infrared and visible spectra (useful for comparison with experiment and for explaining the electronic and magnetic properties of the molecule). It's the whole picture that's valuable, not just the structure - and the more experimental properties you include, the harder it is to fake the whole thing.