Showing papers by "Pavel Hobza published in 1992"

Ab initio second- and fourth-order Møller-Plesset study on structure, stabilization energy, and stretching vibration of benzene⋅⋅⋅X (X=He,Ne,Ar,Kr,Xe) van der Waals molecules

Abstract: The C6v structure of benzene⋅⋅⋅X (X=He, Ne, Ar, Kr, Xe) complexes was investigated with second‐order Mo/ller–Plesset (MP2) theory; for the benzene⋅⋅⋅He the whole potential‐energy surface (PES) was also studied. The stabilization energy of the benzene⋅⋅⋅He was also determined at the fourth‐order Mo/ller–Plesset (MP4) level; the respective MP4 stabilization energy is almost identical with MP2 stabilization energy which is due to the compensation of MP3 and MP4 contributions. The ab initio MP2 intermolecular distances agree nicely for all the complexes studied with the experimental value. While the stabilization energy of benzene⋅⋅⋅He and benzene⋅⋅⋅Ne (67 cm−1; 99 cm−1) is considerably smaller than that of benzene⋅⋅⋅Ar (429 cm−1), the intersystem distance differs less (3.32 A, 3.50 A, 3.53 A). The stabilization energies and intersystem distances for benzene⋅⋅⋅Kr and benzene⋅⋅⋅Xe are 485 and 601 cm−1 and 3.71 and 3.89 A, respectively. The PES of benzene⋅⋅⋅He differs from that of benzene⋅⋅⋅Ar and can be charac...

High level ab initio calculations on acetylene dimer : a prototype for estimation of the accuracy of the benzene dimer stabilization energy

Abstract: High level ab initio calculations (up to MP4/DZ + (2df,2p)) on acetylene dimer permit the evaluation of a highly accurate stabilization energy of the dimer (5.9 kJ/mol) and hence serves as a test case for the error limit for lower level calculations. This error limit was employed to estimate the stabilization energy and enthalpy in the benzene dimer calculation. From this the theoretical value of formation enthalpy at 0 K (11.3 kJ/mol) is obtained which is larger than the corresponding experimental value (6.7 ± 2.1 kJ/mol).

Associates, Clusters, Intermolecular Complexes, Supramolecular Systems: Van der Waals Species

Abstract: This is an article summarizing theoretical studies carried out recently in our laboratory on van der Waals (vdW) species. In contrast to classical molecules, theoretical structure elucidation of vdW molecules nearly always represents a challenge for computational chemists. Results on molecule-molecule complexes (e.g., (H2)2, benzene and benzyne complexes with rare gas atoms, benzene dimer, purine-pyrimidine complexes) and ion-molecule complexes (e.g., H, radical cations of dimers of alkyl halogenides and of alkylated and arylated water) are reviewed. The importance of study of the intersystem vibrational degrees and the role of molecular dynamics in the field of vdW systems in outlined.