Openings

Project Title: Aromaticity and magnetic properties in large conjugated rings

We offer a two-month summer internship at the Quantum Chemistry Development group to work on aromaticity. The call is open for applications until the end of March.

In this work, the candidate will learn how to quantify aromaticity using computational chemistry. She/He/They will get acquainted with concepts like electron delocalization, delocalization error, aromaticity in large macrocycles, as well as the electronic and magnetic aspects of aromaticity.

Since its appearance, the density functional theory (DFT) has experienced a vast development, establishing nowadays as the most employed tool to tackle many different aspects of the electronic structure of molecular systems. The density functional theory is, in principle, an exact method. It works with functionals, which give the energy or other properties in terms of the electron density n(r). Only a small but essential contribution to the energy, the exchange-correlation (XC) energy, thus far remains unknown as a functional of the density and has to be approximated. In this regard, current density functional approximations are a far cry from predictable, and consequently, they do not show the desirable transferability among properties.

Density Functional Theory (DFT) is indisputably the most widely employed electronic structure method, used in chemistry, physics, material science, biology and cross-field specialties. DFT is an exact theory but current density functional approximations (DFAs) fail to account for the breaking of chemical bonds, strongly correlated materials, transition metal systems, magnetic properties or dispersion interactions in excited states. These limitations are connected to the three main open challenges in DFT: large self-interaction errors, proper inclusion of nondynamic correlation and description of noncovalent interactions beyond ad hoc semi-empirical corrections. Despite the proliferation of new DFAs, these issues remain unsolved. In this sense, DFT has reached a dead-end point and it needs fresh innovative ideas and ingredients for a new generation of robust all-purpose DFAs to be developed.

This project presents a genuinely new strategy to construct DFAs in which the exchange-correlation functional is decomposed exactly into nondynamic and dynamic correlation components at different interelectronic domains. The separation breaks the complicated exchange-correlation functional into simpler mathematical objects that are easier to treat. The prospective postdoctoral fellow will work on a project that holds the promise of both providing a more accurate and rigorous description of systems within the fields where DFT is currently applied and extending the scope of application to challenging systems.

Candidates should have a strong background on electronic structure theory, and excellent programming skills. Experience on the development of density functional approximations or other computational chemistry methods will be highly appreciated. The position is for one year with the possibility to extend it up to three years.

Interested candidates should submit an updated CV and a brief statement of interest to Dr. Eduard Matito (ematito@gmail.com). Reference letters are welcome but not indispensable. Very good communications skills in English are required.

Are you interested in research? Do you want to work on the development of electronic structure methods? The DIPC offers a paid internship in Donostia to work with us.

Quantum mechanics provides the framework to treat molecular systems but its exact application for systems with more than two particles remains elusive. In practice, electronic structure simulations rely on approximate computational methods of variable accuracy. The main obstacle towards the accurate description of molecular systems is the so-called electron correlation. One of the most difficult problems in quantum mechanics is the account of strong correlation. Radical systems, bond activation, magnetic compounds, transition metal complexes, among others, suffer from strong correlation and their correct simulation is hampered by the lack of cost-efficient computational methods.

The cost of the electronic structure methods increases importantly with the system size. Among the computational methods available in the literature, density functional theory (DFT) is the one that provides a best comprise between accuracy and computational cost. Unfortunately, current density functional approximations (DFAs) fail to account for strong correlation and there are thus no cost-efficient methods to study large strongly correlated systems. In this sense, the inclusion of strong correlation in DFAs is one of the greatest present challenges in this field.

In this work, the candidate will explore new models of strong correlation designed in our group. These models will be used to retrieve the strong correlation part of the electron-electron interaction in the context of DFT. The models will be tested on the dissociation of diatomic molecules, radicals systems and transition metal complexes.

The candidate should have a basic knowledge on quantum mechanics (assumed in physics and chemistry BSc. students), and be eager to learn the basics of electronic structure theory and DFT.