Evaluation of Charge and Energy Storage in Molecular Nanocapacitors

A model is presented herein for the evaluation of storedchargeand energy in molecular-scale capacitors composed of parallel nanosheets.In this model, the nanocapacitor is exposed to an external electricfield, and the charging process is considered as a three-stage mechanism,including isolated, exposed, and frozen stages, where each stage possessesits own Hamiltonian and wavefunction. In this way, the third stage'sHamiltonian is the same as that of the first stage, while its wavefunctionis frozen to that of the second stage, and consequently, stored energycan be calculated as the expectation value of second stage'swavefunction with respect to the first stage's Hamiltonian.Electron density is then integrated over half-space, i.e., the spaceseparated by a virtual plane located at the middle and parallel toelectrodes, to reveal stored charge on nanosheets. The formalism isapplied to two parallel hexagonal graphene flakes as nanocapacitor'selectrodes, and results are compared with experimental values of similarsystems.