The PERCH approach for 1H and 13C NMR shift prediction is based on a combination of an incremental model with 4D structural descriptors (3D geometry + flexibility) and localized principal component analysis.

The coupling constants, leading also to NOE and COSY-type correlations, are based on empirical equations averaged over the molecular conformational space (the 4th dimension), which is mapped via a Metropolis Monte Carlo search combined with molecular dynamics.

The trajectory is then projected to the time-ensembles of parameters describing molecular electronic properties, geometry, stereo chemistry and solvent accessibility.

Note: Starting from version 2010.1 the prediction is deterministic.