We have evaluated the performance of a set of widely used force fields by calculating the geometries and stabilization energies for a large collection of intermolecular complexes. These complexes are representative of a range of chemical and biological systems for which hydrogen bonding, electrostatic, and van der Waals interactions play important roles. Benchmark energies are taken from the hi...

BACKGROUND The prediction of ligand binding or protein structure requires very accurate force field potentials - even small errors in force field potentials can make a 'wrong' structure (from the billions possible) more stable than the single, 'correct' one. However, despite huge efforts to optimize them, currently-used all-atom force fields are still not able, in a vast majority of cases, even...

We investigate the role of weak clamping forces, typically assumed to be infinite, in carbon nanotube mechanical resonators. Due to these forces, we observe a hysteretic clamping and unclamping of the nanotube device that results in a discrete drop in the mechanical resonance frequency on the order of 5-20 MHz, when the temperature is cycled between 340 and 375 K. This instability in the resona...

We have developed a model for the calculation of van der Waals force for layered systems with axial symmetry. Our result can be applied to compute the cohesion of a carbon nanotube to a substrate, the cohesion between nanotubes, and between shells of multiwall nanotubes. We have obtained unusal power laws for the distance dependence of the many-body van der Waals potential.

We derive the van der Waals energy and pressure in a planar multilayer system with arbitrary number of dissipative films between two half-spaces. A unique feature of this work is that the entire analysis is performed on the real frequency axis instead of summation over Matsubara frequencies on the imaginary frequency axis. The expression we obtain for van der Waals energy is a generalization of...

the ultrasonic velocity, density and viscosity of some schiff bases of 4-amino benzoic acid  were measured in 1,4-dioxane and dimethylformamide at 308.15 k. various acoustical properties such as isentropic compressibility (ks), rao’s molar sound function (rm), the van der waals constant (b), molar compressibility (w), inter molecular free length (lf), relaxation strength (r), internal pressure ...

We show that weakly bound He-containing van der Waals molecules can be produced and magnetically trapped in buffer-gas cooling experiments, and provide a general model for the formation and dynamics of these molecules. Our analysis shows that, at typical experimental parameters, thermodynamics favors the formation of van der Waals complexes composed of a helium atom bound to most open-shell ato...