Welcome to Linnaeus Physics Colloquium, a series of seminars delivered by renowned researchers in physics.
Lecturer: Dr Barbara Brena, Associate Professor at the Division of Materials Theory, Department of Physics and Astronomy, Uppsala University, Sweden
Title: Single molecule magnets: spin manipulation, intermolecular interactions and electronic structure. An overview by ab-initio calculations and beyond.
Place: Kalmar – room N304, Norrgård. Växjö – through link, room D0073, building D. Live – through Adobe Connect, https://connect.sunet.se/cmp-kalmar.
Coffee and buns at 13.45 at Norrgård, room N304.
Organic molecules like 3d transition metal phthalocyanines and porphyrins are among the most promising candidates for applications in molecular electronics and spintronics. It has been shown that the electronic structure and the spin of these compounds can be affected by factors such as ligands and adsorption configurations.
In search of a practically feasible magnetic switching mechanism, we have previously studied how the molecular spin in porphyrins and phthalocyanines is affected by the interaction with magnetic substrates as well as by the adsorption of gases.  Our studies are based on ab-initio calculations in collaboration with soft x-ray spectroscopy. Aiming to understand the magnetic behaviour in novel supramolecular architectures, we have also analyzed the magnetic coupling and moment in molecular sandwiches of these compounds like FePc and MnPc.
It is known that Density functional theory (DFT) in the generalised gradient approximation (GGA) and in the local density approximation (LDA) has big limitations in properly describing highly correlated and localized d-electrons. We have therefore thoroughly studied the effect of the Hubbard U method, which accounts for the intra-atomic Coulomb interactions , on the electronic structure of several 3d phthalocyanines .
In addition, with the goal to reveal in detail the still debated electronic structure of such molecules, we have developed a computational scheme for the first-principles modelling of the L2,3 edges X-ray Absorption Spectra (XAS), based on the combination of Density Functional Theory plus Dynamical Mean Field Theory (DFT+DMFT) and Multiplet Ligand Field Theory (MLFT). The method has been so far successful in the simulation of the L2,3 edge XAS of transition Metal Oxides, and the coming developments will address several different materials including 3d metal phthalocyanines. 
 S. Bhandary, et al. Rev B, 88. (2013) 024401. D. Klar, et al. Phys. Rev. B 88. (2013) 224424. H. C. Herper, et al. Phys. Rev. B 89 (2014) 085411. H. Herper, B. Brena, published online. DOI: 10.1063/1.4917242
 Liechtenstein, A. I.; Anisimov, V. I.; Zaanen, J. Phys. Rev. B 1995, 52, R5467-R5470. Dudarev, S. L.; Botton, G. A.; Savrasov, S. Y.; Humphreys, C. J.; Sutton, A. P. Phys. Rev. B 1998, 57, 1505-1509.
 I.E. Brumboiu, S. Haldar, J. Lüder, O. Eriksson, H.C. Herper, B. Brena, B. Sanyal, J. Chem. Theory Comput., 2016, 12 (4), pp 1772–1785, DOI:10.1021/acs.jctc.6b00091.
I.E. Brumboiu, S. Haldar, J. Lüder, O. Eriksson, H.C. Herper, B. Brena, B. Sanyal, in manuscript.
 Johann Lüder, Johan Schött, Barbara Brena, Maurits W. Haverkort, Patrik Thunström, Olle Eriksson, Biplab Sanyal, Igor Di Marco, and Yaroslav O. Kvashnin, Phys. Rev. B 96, 245131 (2017).