  A practical method utilising three-dimensional image pattern matching is
proposed which, in principle, is capable of unambiguous determination of the
types and positions of atoms in small molecules from defocus series collected
at only a few different angular orientations of the molecule. Numerical tests
of the method are presented using multislice calculations of defocus series of
small biological molecules. The proposed technique can in future gain from
Bayesian or machine-learning approaches and is likely to be useful in cryogenic
electron microscopy.
