Successes and Challenges of Ab Initio Quantum Chemistry
Ab initio quantum chemistry involves the calculation of molecular properties and interactions without any experimental input, i.e. directly from the underlying physics as described by quantum mechanics. This approach, exemplified by popular and powerful methods such as CCSD(T), has had many successes in reproducing experimental results with high accuracy, particularly in the fields of thermodynamics, kinetics, and molecular spectroscopy. I will present several of these success stories, in particular from my own experience, and discuss their practical implications.
However, purely ab initio methods are not without their failures as well. In particular, I will show how coupled cluster methods currently have difficulty in reproducing spectroscopic features in the X-ray region in a cost-effective manner. I will briefly examine the potential benefits of ab initio quantum chemistry to the X-ray problem, as well as the fundamental causes of coupled cluster's failure. Lastly, I will discuss some ways in which these shortcomings might be addressed and some interesting future applications in both the gas and condensed phases.
