 In chemical systems, slightly more sophisticated versions of this factor can obtain 80–90% of the correlation energy (see electronic correlation) with less than 30 parameters.In comparison, a configuration interaction calculation may require around 50,000 parameters to reach that accuracy, although it depends greatly on the particular case being considered.In addition, VMC usually scales as a small power of the number of particles in the simulation, usually something like "N"2−4 for calculation of the energy expectation value, depending on the form of the wave function.