Application of variational reduced-density-matrix theory to organic molecules

摘要

Variational calculation of the two-electron reduced-density matrix(2-RDM),using a new first-order algorithm [D.A.Mazziotti,Phys.Rev.Lett.93,213001(2004)],is applied to medium-sized organic molecules.The calculations reveal systematic trends in the accuracy of the energy with well-known chemical concepts such as hybridization,electronegativity,and atomic size.Furthermore,correlation energies from hydrocarbon chains indicate that the calculation of the 2-RDM subject to two-positivity conditions is size extensive,that is,the energy grows linearly with the number of electrons.Because organic molecules have a well-defined set of functional groups,we employ the trends in energy accuracy of the functional groups to design a correction to the 2-RDM energy for an arbitrary organic molecule.We apply the 2-RDM calculations with the functional-group correction to a large set of organic molecules with different functional groups.Energies with millihartree accuracy are obtained both at equilibrium and nonequilibrium geometries.