A global potential energy surface for the water dimer is constructed using the modified Shepard interpolation scheme of Collins et al. According to this interpolation scheme, the energy at an arbitrary geometry is expressed as a weighted sum of Taylor series expansions from neighboring data points, where the energy and derivative data required are obtained from ab initio calculations. For some ...

We apply the relativistic configuration-interaction valence-bond method to calculate various characteristics of the alkali-metal RbCs dimer. These include the electronic potentials and transition dipole moments between the ground and first excited states and permanent dipole moments of the X 1sigma+ and a 3sigma+ states of the ground configuration. In addition, we estimate the lifetime of the r...

Enzymes which hydrolyse ATP cause an exchange of 180 of labelled Pi in the presence of ADP. A theory for the evaluation of rate constants from an observation of the time dependence of the concentration of the various Pi species is presented. Application to the 180 exchange catalysed by myosin SI as observed by 31P-NMR shows excellent agreement with values o f the rate constants determined earlier.

The relativistic configuration interaction valence-bond method has been used to calculate permanent and transition electric dipole moments of the KRb heteronuclear molecule as a function of internuclear separation. The permanent dipole moment of the ground-state X S potential is found to be 0.30~2! ea0 at the equilibrium internuclear separation with excess negative charge on the potassium atom....

The existence and stability of atoms rely on the fact that neutrons are more massive than protons. The measured mass difference is only 0.14% of the average of the two masses. A slightly smaller or larger value would have led to a dramatically different universe. Here, we show that this difference results from the competition between electromagnetic and mass isospin breaking effects. We perform...

Excitation of HeNe by synchrotron light just below the frequency of the 1s → 3p transition of isolated He has been recently shown to be followed by resonant interatomic Coulombic decay (ICD). The vibrationally resolved widths of the ICD states were extracted with high precision from the photoion spectra. In this paper, we report the results of ab initio calculations of these widths. We show tha...

In this work, we have calculated ab initio the vibrational modes and the phonon frequencies for the SiC (100) surfaces. Our results are in good agreement with the available experimental data whenever this comparison is possible: in fact, most of our obtained results are predictions. For the accepted models of the C-terminated surfaces in the c(2!2) reconstruction, while in the bridge-dimer mode...

We explore the use of ab initio, density-functional methods for the study of large-scale materials problems. Three examples are presented: (i) the interplay of surface and edge reconstructions in long silicon nanowires, where we examine the effects on electrical and mechanical properties; (ii) the calculation of solvation effects based on ab initio dielectric models, where we derive the dielect...

The density functional based calculations of the electronic structure of YMnO3 are performed for selected spin configurations and from the differences of the total energies the exchange integrals are determined. To improve the description of strongly correlated 3d electrons of Mn the LDA + U method is employed. The strongest exchange interaction is found between the nearest neighbor Mn spins, t...

Several research groups have recently reported ab initio calculations of the melting properties of metals based on density functional theory, but there have been unexpectedly large disagreements between results obtained by different approaches. We analyze the relations between the two main approaches, based on calculation of the free energies of solid and liquid and on direct simulation of the ...