The harmonic approximation to transition state theory simplifies the problem of calculating a chemical reaction rate to identifying relevant low energy saddle points in a chemical system. Here, we present a saddle point finding method which does not require knowledge of specific product states. In the method, the potential energy landscape is transformed into the square of the gradient, which c...

We describe a procedure to develop a fitting basis for molecular potential energy surfaces (PESs) that is invariant with respect to permutation of like atoms. The method is based on a straightforward symmetrization of a primitive monomial basis and illustrated for several classes of molecules. A numerically efficient method to evaluate the resulting expression for the PES is also described. The...

The accuracy of excited states calculated with Kohn-Sham density functional theory using the maximum overlap method has been assessed for the calculation of adiabatic excitation energies, excited state structures, and excited state harmonic and anharmonic vibrational frequencies for open-shell singlet excited states. The computed Kohn-Sham adiabatic excitation energies are improved significantl...

The complex conformational change from B-DNA to Z-DNA requires inversion of helix-handedness. Multiple degrees of freedom are intricately coupled during this transition, and formulating an appropriate reaction coordinate that captures the underlying complexity would be problematic. In this contribution, we adopt an alternative approach, based on the potential energy landscape perspective, to co...

A cluster is a group of identical molecules or atoms loosely bound by inter-atomic forces. The optimal geometry minimizes the potential energy — usually modelled as the Lennard-Jones potential — of the cluster. The minimization of the Lennard-Jones potential is a very difficult global optimization problem with extremely many local minima. In addition to cluster problems, the Lennard-Jones poten...

equilibrium geometry, electronic structures, and vibrational modes of cob8- were investigated in the pbepbe/6-311+g(d,p) level of theory. the nucleus independent chemical shift (nics) analysis and magnetizability values were used for studying of aromaticity in cob8-. the effects of different solvents on the structure and frontier orbital energies were calculated using the polarizable continuum ...

minimum-energy CMOS S. Hanson B. Zhai K. Bernstein D. Blaauw A. Bryant L. Chang K. K. Das W. Haensch E. J. Nowak D. M. Sylvester Energy efficiency has become a ubiquitous design requirement for digital circuits. Aggressive supply-voltage scaling has emerged as the most effective way to reduce energy use. In this work, we review circuit behavior at low voltages, specifically in the subthreshold ...

Octahedral Fe(2+) molecules are particularly interesting as they often exhibit a spin-crossover transition. In spite of the many efforts aimed at assessing the performances of density functional theory for such systems, an exchange-correlation functional able to account accurately for the energetic of the various possible spin-states has not been identified yet. Here, we critically discuss the ...

Smooth potential energy surfaces and analytic gradients are obtained for cavitation, dispersion, and repulsion free energies in the polarizable continuum model using the fixed points with variable areas (FIXPVA) tessellation scheme. In addition, it is shown that FIXPVA can reproduce the standard GEPOL results to within 1 kcal/mol.

We consider the thermally activated quantum diffusion of a molecular dimer in a periodic surface potential by means of a time-dependent wave packet method. We show that the potential energy surface resulting from the interplay of intradimer and dimer-surface interactions can lead to resonant states and predict high tunneling probabilities at specific, below barrier, energies that depend also on...