PhD conferral Stefan Vuckovic



Aula, Vrije Universiteit Amsterdam

Fully Nonlocal Exchange-Correlation Functionals from the Strong-coupling limit of Density Functional Theory

Stefan Vuckovic

Prof. P. Gori Giorgi and copromotor Dr M.W.J. Seidl

Amsterdam Institute for Molecules, Medicines and Systems


PhD conferral

Fully Nonlocal Exchange-Correlation Functionals from the Strong-coupling limit of Density Functional Theory

Density functional theory methods are nowadays routinely used in most of chemistry branches for guiding and understanding experiments and for designing new drugs and materials. With an accuracy that is often competitive with much more expensive many-body methods, DFT calculations provide a relatively fast way for obtaining quantum-mechanical description of electronic motions that govern chemical principles.

Success and Failures of DFT
The story behind the most popular DFT approaches has been very successful and the corresponding articles are some of the most cited articles ever. Despite this widespread success, there are still situations when present DFT methods can give even qualitative failures. This happens when the interaction between electrons plays a prominent role, i.e. when a system of interest is strongly correlated. Strong correlation is omnipresent in chemistry and it plays a very important role when it comes to chemistry of transition metals and processes that are accompanied by bond forming and breaking. The inability of DFT to describe strongly correlated systems and processes hampers its overall predictive power and usability. Many people attempted to address the problem of strong correlation within the present mainstream framework of DFT, but such efforts have not been fruitful so far.

Departure from the mainstream framework of DFT
In his thesis, Stefan Vuckovic addresses the problem of strong correlation within DFT from a different standpoint. Together with his co-workers, Vuckovic looked at the limit of infinite electronic correlation, the so-called strongly-interacting limit (SIL). This limit was introduced by M. Seidl and later extensively studied in the group of author’s supervisor, Paola Gori-Giorgi. During the first stage of his PhD, Vuckovic and co-workers explored the routes for using SIL in chemistry and obtained highly nontrivial SIL quantities for chemical systems. They combine these quantities with those from the weakly-interacting limit to propose methods that do not suffer from a bias towards a particular correlation regime, as most of the other DFT approaches.

That research stage taught them that simple integrals of the electron density, a one-body quantity that gives a probability of finding electrons at a given point of space, encodes the information on the pair-interaction between electrons. They further utilized this observation to simplify and adjust the strong-interaction limit for applying it to the finite, i.e. physical, electronic interaction. Along these lines they have proposed several efficient and rather accurate approaches.

Vuckovic and co-workers also used their methodology to make contributions to the fundamentals of DFT. They set rigorous constants appearing in the famous Lieb-Oxford bound and proposed new lower bounds to correlation energy. They also defined correlation indicators that can be used for quantitative measures of electronic correlation in a given molecular region.

Graphical_abstract_VuckovicPhD Defense
Vuckovic has performed his PhD research in the Theoretical Chemistry Department under the supervision of Paola Gori-Giorgi. He will defend his PhD Thesis entitled ”Fully Nonlocal Exchange-Correlation Functionals from the Strong-coupling limit of Density Functional Theory” on the 14th of November 2017 at 11:45 in the auditorium of Vrije Universisteit Amsterdam.

Selected references

Vuckovic, Stefan, Lucas O. Wagner, André Mirtschink, and Paola Gori-Giorgi. "Hydrogen Molecule Dissociation Curve with Functionals Based on the Strictly Correlated Regime." Journal of chemical theory and computation 11, no. 7 (2015): 3153-3162.

Seidl, Michael, Stefan Vuckovic, and Paola Gori-Giorgi. "Challenging the Lieb- Oxford bound in a systematic way." Molecular Physics 114, no. 7-8 (2016):1076-1085.

Vuckovic, Stefan, Tom JP Irons, Andreas Savin, Andrew M. Teale, and Paola Gori-Giorgi. "Exchange–correlation functionals via local interpolation along the adiabatic connection." Journal of chemical theory and computation 12, no. 6 (2016): 2598-2610.

Vuckovic, Stefan, Tom JP Irons, Lucas O. Wagner, Andrew M. Teale, and Paola Gori-Giorgi. "Interpolated energy densities, correlation indicators and lower bounds from approximations to the strong coupling limit of DFT." Physical Chemistry Chemical Physics 19, no. 8 (2017): 6169-6183.

Vuckovic, Stefan, and Paola Gori-Giorgi. "Simple fully non-local density functionals for the electronic repulsion energy." The Journal of Physical Chemistry Letters (2017)