Hydrogen bonding between base pairs in nucleic acids is a key determinant of their structures. We have examined the distance dependence of the hydrogen bonding of AT-WC (Watson-Crick), GC-WC, and AT-H (Hoogsteen) base pairs using ab initio quantum mechanics, LMP2/cc-pVTZ(-f) energies at HF/cc-pVTZ(-f) optimized geometries. From these curves, we have extracted Morse potentials between the H atom...

A global double many-body expansion potential energy surface is reported for the electronic ground state of H2S by fitting accurate ab initio energies calculated at the multireference configuration interaction level with the aug-cc-pVQZ basis set, after slightly correcting semiempirically the dynamical correlation by the double many-body expansion-scaled external correlation method. The functio...

The dissociative adsorption of hydrogen on Pd(100) has been studied by ab initio quantum dynamics and ab initio molecular dynamics calculations. Treating all hydrogen degrees of freedom as dynamical coordinates implies a high dimensionality and requires statistical averages over thousands of trajectories. An efficient and accurate treatment of such extensive statistics is achieved in two steps:...

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 ...

Ab initio calculation based on density function theory (DFT) is an accurate and efficient method for modelling material properties. It is performed by solving the Shrödinger equations with a few assumptions to obtain the physical properties of the system. It is very computational demanding when dealing with large systems or longtime simulations. Developing empirical potentials on the basis of a...

The authors present a new potential energy curve, electric dipole moment function, and spin-orbit coupling function for OH in the X 2Pi state, based on high-level ab initio calculations. These properties, combined with a spectroscopically parametrized lambda-type doubling Hamiltonian, are used to compute the Einstein A coefficients and photoabsorption cross sections for the OH Meinel transition...

Ab initio techniques based on density functional theory in the projector-augmented-wave implementation are used to calculate the free energy and a range of other thermodynamic properties of liquid iron at high pressures and temperatures relevant to the Earth’s core. The ab initio free energy is obtained by using thermodynamic integration to calculate the change of free energy on going from a si...

Explicit or implicit expressions of potential energy surfaces (PES) represent the basis of our ability to simulate condensed matter systems, possibly understanding and sometimes predicting their properties by purely computational methods. The paper provides an outline of the major approaches currently used to approximate and represent PESs and contains a brief discussion of what still needs to ...