Theoretical radiochemistry is nothing but the overlap between theoretical chemistry and radiochemistry. Though radiochemistry may concern the whole periodic table (every elements display unstable isotopes), a special focus is made on the radioelements, which by definition do not display any stable isotope, and are typically heavy elements.
A key objective is to take the best profit of computational chemistry calculations for interpreting and predicting the outcomes of “hot” experiments. Note that on the one side, radioactivity provides specific ways of detecting matter (e.g. counting), but on the other one it may severely limit the list of experiments that may be practically accessible.
Thus, any grounded information coming out of reliable calculations is particularly welcomed, and sometimes strictly necessary to propose a decent interpretation of the data. Theoretical radiochemistry thus concerns methodological development, methodological studies, joint theory/experiment studies and as an ultimate goal theoretical predictions.
Here we aim at determining the molecular structures of new chemical species, describing their electronic structures (in particular determining the “oxidation state” of the metal), and computing reaction energies. Complementary mass spectrometry and/or infra-red spectroscopy experiments may be performed by collaborators.
Here we aim at interpreting or predicting the outcomes of spectroscopy experiments, be them in the gas phase or in solution, and absorption (from infra-red to X-ray) or fluorescence spectroscopies. Excitation energies and/or spectra may be computed. Naturally, complementary experiments may be performed by collaborators.
Chemistry in solution
Here we aim at identifying new chemical species, determining their molecular and electronic structures in solution (these may drastically differ from the gas-phase ones), and computing equilibrium constants. Complementary chromatography, liquid-liquid extraction and/or electromobility experiments may be performed by collaborators.
Here we aim at developing and applying original chemical bonding analyses that are safely applicable to heavy-element systems, meaning that the underlying level of theory must be relativistic. Various bonding indicators are looked for, effective bond orders, topological descriptors as well as outcomes of valence bond analyses.
Physical properties may be derived from knowledge on many-particle states. These properties may be energy and/or wave function dependent. Thus, quantum mechanical approaches may be the route toward computing physical properties. By definition, these are observables, meaning that comparison of computational data with experiment is expected.
In theory, this seems quite straightforward. However, the interpretation of the experimental data often makes use of simple models, which may drastically differ from the more elaborated computational ones. Thus, a fair comparison of computational and experimental data may not be that straightforward and require the extraction of the same effective parameters than in the experimental analysis.
As a theoretical chemist and a molecular devotee, I am more inclined to work on molecular many-electron states and thus on molecular electronic properties. Note that I also use my molecular perspective to tackle condensed matter problems by means of the embedded cluster approach.
Here we aim at defining model Hamiltonians from the outcomes of quantum mechanical calculations by means of the effective Hamiltonian theory. Emphasis is put on the zero-field splitting, i.e. the degeneracy lift of energy levels in the absence of an external magnetic field. Currently, molecular systems with one or several active magnetic sites are studied.
Excited states may be associated with a wide range of photophysical processes such as luminescence. Understanding these processes requires identification and characterization of the involved electronic states as well as their potential couplings via the spin-orbit coupling operator. In this theme, I work within the framework of projects of the CTI team.