Theoretical characterization of structural and energetical properties of water clusters, by means of a simple polarizable water Hamiltonian (original) (raw)

Electric field effects on water clusters (n=3–5): Systematic ab initio study of structures, energetics, and transition states

The Journal of Chemical Physics, 2006

The structures, energetics, and transition states of water clusters ͑trimer to pentamer, n =3-5͒ are investigated as a function of electric field by using ab initio calculations. With an increasing strength of the field, the most stable cyclic structures of trimer, tetramer, and pentamer open up to align their dipole moments along the direction of the field. For the lower strength ͑below 0.3 V / Å͒ of the electric field, the dipole moment of each water monomer is along the same direction with the field, while it retains the cyclic structure. For the higher strength of the field, to have a higher dipole moment for the cluster along the field direction, each cyclic structure opens up to form a linear chain or "water wire." We have investigated the transition state structures between the cyclic and linear forms for the field strengths of 0.3-0.4 V / Å where both cyclic and linear forms are energetically comparable.

Structural Mathematical Models of Water Clusters Regarding the Energy of Hydrogen Bonding

Nanotechnology research and practice, 2015

In this review it is reported about the research on the structure of intermolecular water cyclic associates (clusters) with general formula (Н2О)n and their charged ionic clusters [(Н2О)n] + and [(Н2О)n]-by means of computer modeling and spectroscopy methods as 1 Н-NMR, IR-spectroscopy, DNES, EXAFS-spectroscopy, X-Ray and neurons diffraction. The computer calculation of polyhedral nanoclusters (Н2О)n, where n = 3-20 are carried out. Based on this data the main structural mathematical models describing water structure (quasicrystalline, continious, fractal, fractal-clathrate) have been examined and some important physical characteristics were obtained. The average energy of hydrogen bonding (EH…O) between Н2О molecules in the process of cluster formation was measured by the DNES method compiles-0,1067±0,0011 eV. It was also shown that water clusters formed from 2 H2О were more stable, than those ones from Н2О due to isotopic effects of deuterium.

A Density Functional Theory for Studying Ionization Processes in Water Clusters

The Journal of Physical Chemistry A, 2011

A generalized Kohn-Sham (GKS) approach to density functional theory (DFT), based on the Baer-Neuhauser-Livshits range-separated hybrid, combined with ab initio motivated range-parameter tuning is used to study properties of water dimer and pentamer cations. The water dimer is first used as a benchmark system to check the approach. The present brand of DFT localizes the positive charge (hole), stabilizing the proton transferred geometry in agreement with recent coupled-cluster calculations. Relative energies of various conformers of the water dimer cation compare well with previously published coupled cluster results. The GKS orbital energies are good approximations to the experimental ionization potentials of the system. Low-lying excitation energies calculated from time-dependent DFT based on the present method compare well with recently published high-level "equation of motion-coupled-cluster" calculations. The harmonic frequencies of the water dimer cation are in good agreement with experimental and wave function calculations where available. The method is applied to study the water pentamer cation. Three conformers are identified: two are Eigen type and one is a Zundel type. The structure and harmonic vibrational structure are analyzed. The ionization dynamics of a pentamer water cluster at 0 K shows a fast <50 fs transient for transferring a proton from one of the water molecules, releasing a hydroxyl radical and creating a protonated tetramer carrying the excess hole.

Structure and Energetics of Ionized Water Clusters:(H2O) n+, n= 2-5

Energetics and geometrical structures of neutral, (H 2 O) n , and ionized, (H 2 O) n + , water clusters, with n ) 2-5, are investigated using local-spin-density functional electronic structure calculations with exchange-correlation gradient corrections. While the ground-state structures of the neutral clusters are hydrogen-bonded cyclic ones, those of the molecular ions are noncyclic. The lowest energy isomers of the ionized (H 2 O) n + clusters contain a hydrazine-like fragment, (H 2 OOH 2 ) + , hydrogen-bonded to the extra water molecules. Higher energy isomers of the cluster ions are based on hydrogen bonding to a disproportionated fragment, (H 3 O) + OH.

Structural Models of Water and Structuring of Nano-clusters Regarding the Energies of Hydrogen Bonds

Journal of Medicine, Physiology and Biophysics, 2015

In this review it is reported about the research on the structure of intermolecular water cyclic associates (clusters) with general formula (Н 2 О) n and their charged ionic clusters [H + (Н 2 О) n ] + and [OH-(Н 2 О) n ]by means of computer modeling and spectroscopy methods as 1 Н-NMR, IR-spectroscopy, NES, DNES, EXAFSspectroscopy, X-Ray and neurons diffraction. The computer calculation of polyhedral nanoclusters (Н 2 О) n , where n = 3-20 are carried out. Based on this data the main structural mathematical models describing water structure (quasi-crystalline, continuous, fractal, fractal-clathrate) have been examined and some important physical characteristics were obtained. The average energy of hydrogen bonding between Н 2 О molecules in the process of cluster formation was measured by the DNES method compiles-0.1067 ± 0.0011 eV. It was also shown that water clusters formed from D 2 О were more stable, than those ones from Н 2 О due to isotopic effects of deuterium.

Molecular-dynamics simulations of water clusters

Physica E: Low-dimensional Systems and Nanostructures, 2000

The local minimum geometries and corresponding energy values of water clusters, [(H2O)n, n = 2-8]; have been investigated by using the molecular dynamics simulation method. In the simulations two di erent potential energy functions of central-force model, CF and CF2, have been used. Particular attention was paid to investigate the e ectiveness of these two empirical potential energy functions. CF has been used for n = 2 only, whereas CF2 has been used for n = 2-8. The cage structure of the water clusters appear for n¿6.

Structure and some properties of small water clusters

Journal of Structural Chemistry, 1994

The energies and structures of many small water clusters (H20)n (n = 8-26) are calculated using the atom-atom potential functions suggested earlier. For each n, several stable configurations were found that differ in the number of H-bonds and in the topology of the graphs formed by such bonds. The clusters in which the molecules lie at the vertices of convex polyhedra have the lowest-energy but other configurations may have close or even lower energies. For the most stable clusters, the energy dependence on n is close to linear. At 300 K, the mean energies of the clusters behave similarly. Monte-Carlo simulations showed that the clusters undergo pseudomelting at approximately 200 K.

Electron binding energies of water clusters: Implications for the electronic properties of liquid water

Chemical physics letters, 2006

Green's function (GF) calculations for the valence electron binding energies of water clusters (H2O)(2-8) are reported. The results are compared with experiment for H2O and (H2O)(2), and with Hartree-Fock and Kohn-Sham calculations with an exchange-correlation functional parametrized to reproduce electronic properties of the dimer. For the liquid, sequential Monte Carlo/GF calculations lead to estimates of the outermost electron binding energy (11.59 +/- 0.12eV) and of the water conduction band edge (V-0) as -0.79 +/- 0.08 eV. Our predictions agree with experimental and recent theoretical results and support that the water electron affinity (-V-0) is smaller than the typical literature value (1.2 eV).

Protonated water clusters described by an empirical valence bond potential

The Journal of Chemical Physics, 2005

The properties of low-lying stationary points on the potential energy surfaces of singly protonated water clusters ͑H 2 O͒ n H + , are investigated using an empirical valence bond potential. Candidate global minima are reported for n =2-4, 8, and 20-22. For n = 8, the variation in the energies and structures of low-lying minima with the number of valence bond states included in the model is studied. For n = 4 and 8, disconnectivity graphs are also reported and are compared to results for the equivalent neutral water clusters as described by the rigid TIP3P potential. For the larger clusters, n = 20-22, the structural properties of the low energy minima are compared with recently published spectroscopic data on these systems. The observed differences between the n = 20 and n = 21 systems are qualitatively reproduced by the model potential, but the similarities between the n = 21 and n = 22 systems are not.