Structures, enthalpies of formation, and ionization energies for the parent and binary mixed carbon, silicon, nitrogen, and phosphorus cubane derivatives: A G4MP2 theoretical study

Abstract

Gas phase standard state (298.15 K, 1 atm) structures, enthalpies of formation, and ionization energies (IEs) were calculated at the G4MP2 composite method level of theory for the parent and binary mixed carbon, silicon, nitrogen, and phosphorus cubane derivatives. Increasing nitrogen content increases the enthalpies of formation for the carbon-nitrogen, nitrogen-phosphorus, and silicon-nitrogen binary cubanes, with the opposite enthalpies of formation trend for increasing phosphorus content within the carbon-phosphorus, nitrogen-phosphorus, and silicon-phosphorus derivatives. Varying carbon/silicon content in the carbon-silicon cubanes results in no general trends for enthalpies of formation. Isomerization enthalpies within the homolog groups having more than one isomer vary widely with atomic composition and substitution patterns. Increasing nitrogen content of the carbon-nitrogen and nitrogen-phosphorus derivatives increases the IE, increasing silicon content in the carbon-silicon cubanes and phosphorus content of the carbon-phosphorus cubanes decreases the IE, while no IE clear trends are evident based on relative atomic content for the silicon-nitrogen and silicon-phosphorus compounds. The binary mixed carbon, silicon, nitrogen, and phosphorus cubane derivatives are predicted to display potentially tunable thermodynamic stability and redox behavior depending on the atom identities and relative positions.