ABINITIO STUDIES OF THE WATER DIMER USING LARGE BASIS-SETS - THE STRUCTURE AND THERMODYNAMIC ENERGIES

Ab initio calculations with various large basis sets have been performed on the water dimer in order to study the structure, energetics, spectra, and electrical properties. As a reference system, the calculations of the water monomer were also performed. The second order Moller-Plesset perturbation theory (MP2) using a large basis set (O:13s,8p,4d,2f/H:8s,4p,2d) well reproduces various water monomer experimental data except for the somewhat underestimated absolute energy and hyperpolarizability. The monomer energy calculated with the fourth-order Moller-Plesset perturbation theory (MP4) with the above basis set is -76.407 hartrees, which is only 0.073 hartree above the experimental energy. To compare the theoretical and experimental dimer structures and thermal energies accurately, we summarized the quantum statistical thermodynamic quantities with corrections for anharmonic vibration, rotation, rotation-vibration coupling, and internal rotation. With the correction for the anharmonic binding potential and rotation, the predicted interoxygen distance of the dimer is 2.958 angstrom, which is so far the closest to the experimental value approximately 2.976 angstrom. The predicted dimer dipole moment is 2.612 D, which is the first agreement with experiment (2.60-2.64 D). The predicted frequency shift of the dimer with respect to the monomer is in good agreement with experiment. With the MP2 calculation using the large basis set, the basis set superposition error correction (BSSEC) of the dimer is only 0.33 kcal/mol, which is by far the smallest among the MP2 results reported. Without BSSEC, the predicted binding energy, enthalpy, free energy, and entropy are all in good agreement with experiment within the error bounds, whereas with BSSEC, some of them seem to be slightly off the experimental error bounds. Nevertheless, the results with BSSEC can be more reliable than those without BSSEC.open11223sciescopu

Molecular dynamics simulations of liquid water using the NCC ab initio potential

International audienceWe present a molecular dynamics simulation of 512 water molecules based on a new ab initio potential. The new potential, called the NCC potential, is an extension of the MCY potential with explicit incorporation of the many-body effects due to polarization. From the MD configurations of a 32 ps simulation with a time step of 0.5 fs, we have calculated the radial pair correlation functions, the X-ray and neutron scattering intensities, the power spectrum of translational and rotational velocity autocorrelation functions, IR spectra, evaporation energy, specific heat, self-diffusion coefficient, NMR relaxation time, sound modes, time-of-flight, and the density of states. A comparison with available experimental data reveals that the use of the NCC potential results in an accurate prediction of a wide spectrum of static and dynamic properties of liquid water

Umweltfreundliche Moebel. Teilvorhaben: Modellhaftes Stoffstrommanagement Wohnmoebel Schlussbericht

SIGLEAvailable from TIB Hannover: F02B447 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman