ANHARMONIC-FORCE FIELD OF FORMAMIDE - A COMPUTATIONAL STUDY

Vibrational energies of HCONH2 and DCONH2 molecules are calculated and compared to experiment. Rotational constants of formamide and water molecules are calculated for several vibrational states. The anharmonic force fields are calculated ab initio on HF and MP2 levels and using local and nonlocal density functional theory. Possible applications of DFT anharmonic force field in a prediction of vibrational properties are discussed. Dipolar derivatives are calculated to second order on the HF level. The phase integral quantum concept is introduced as a tool for an efficient diagonalization of the vibrational Hamiltonian.