Theoretical investigation of cis‐ and trans‐nitric oxide dimers with ab initio and density functional Gaussian‐type orbital approach

Abstract Structures and total energies of the cis ‐NO dimer, the trans ‐NO dimer, and the NO monomer were calculated by ab initio methods ( UHF , UMP 2, and MP 3) and density functional theory methods ( LSDA and BLYP ) with different basis sets [from 3‐21G* to 6‐311++(3 df ,3 pd )]. The system is especially hard to model because two NO molecules are weakly associated in a dimer that has a very long NN bond. The results obtained by different methods are compared and the necessity of correlational methods for studying these systems is discussed. © 1995 John Wiley & Sons, Inc.