Electronic structure and molecular dynamics of breakingthe RO—NO_2bond

摘要

Decomposition of energetic molecules such as pentaerythritol tetranitrate is accompanied byextensive changes in their electronic configuration and thus is challenging for ab initio Born–Oppenheimer molecular dynamics simulations. The performance of single-determinant methods (inparticular, density-functional theory) is validated on electronic structure and molecular dynamicssimulations of RO–NO_2bond dissociation in a smaller nitric ester, ethyl nitrate. Accuratedescription of dissociating molecule requires using unrestricted, spin-symmetry-broken orbitals.However, the iterative self-consistent field procedure is prone to convergence failures in thebond-breaking region even if robust convergence algorithms are employed. As a result, moleculardynamics simulations of unimolecular decomposition need to be closely monitored and manuallyrestarted to ensure seamless transition from the closed-shell to open-shell configuration.