Picture level benchmark

Our philosophy was instead top-down . We decomposed the molecular TAE (total atomization energy TAEe at the bottom of the well, TAEo at absolute zero) into all components that can reasonably affect it at the kl/mol level. Then we carried out exhaustive benchmark calculations on each component separately for a representative training set of molecules. Finally, for each component separately, we progressively introduced approximations up to the point where reproduction of that particular component started deteriorating to an unacceptable extent. Thus, experimental data entered the picture only at the validation stage, not at the design stage. 

Huge systems like DNA are not accessible by traditional first-principles algorithms as employed in electronic structure theory. However, first-principles electronic structure methods are often needed in order to achieve the necessary level of accuracy for either benchmark calculations that may serve as a reference or in cases where a detailed molecular picture is mandatory. It is therefore desirable to further develop ab initio and DFT methods in the context of multiscale modeling [147]. Examples for extended first-principles CPMD calculations on electronic and optical properties of DNA and on the reactivity of radical cations can be found in Refs. [148-150]. 

Using the H-atom Rydberg tagging time-of-flight crossed molecular beam technique, Dr. Ren studied the reaction resonance and non-adiabatic effects at a full quantum resolved level in the F + H2 system. Through state-to-state resolved experiments, he provided the first conclusive evidence of reaction resonances in the F %,2) + H2 -> HF + H reaction. The dramatic difference between the dynamics for the F( P3/2) + H2(j = 0,1) reactions represents a textbook example of the role of reactant rotational level in resonance phenomena in this benchmark system. Dr. Ren has also carried out a very high-resolution experimental study on the dynamics of the isotope substituted reaction, F( P3/2) -I- HD -> HF -I- D, with spectroscopic accuracy (a few cm ). These findings provided a very clear physical picture for reaction resonances in this benchmark system, which has eluded us for more than 30 years. 

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