### DEPARTMENT of chemistry and biochemistry, florida state university

## Large-Scale CASSCF Calculations with the Variational Two-Electron Reduced Density Matrix Method

##### Tuesday, November 24, 2015 at 9:00 AM

##### 325 EBERLY HALL

The use of conventional multi-configuration interaction methodologies to study the electronic structure of strongly-correlated molecules and materials is limited by the size of the active space of interest. The variational two-electron reduced density (v2RDM) method is a viable alternative for the analysis of the electronic structure of molecules and materials. However, the v2RDM method is not well known to the computational chemistry community nor is it implementation readily available, which makes it difficult to assess its utility. Using the boundary point semidefinite optimization method, an open-shell implementation of the v2RDM method is implemented in PSI4. The performance of our implementation is evaluated by comparing the energies of selected molecules to those obtained using competing wave-function-based methodologies. We also predict the energy difference between different spin states using model systems, including a linear hydrogen chain and linear poly-cyclic aromatic hydrocarbons (acenes). The largest calculation on dodecacene (12 linearly fused benzene rings) is comparable to the complete-active-space self-consistent field computation with 50 electrons in 50 orbitals using the Dunning triple zeta basis set on all the centers.