לוח שנה משולב

The method of dispersion correction as an add-on to standard Kohn-Sham density functional theory (DFT-D [1]) has been refined regarding higher accuracy, broader range of applicability and less empiricism [2]. The main new ingredients are atom-pair wise specific dispersion coefficients and cut-off radii that are both computed from first principles (TD)DFT for all elements up to Z=94. Geometry dependent information is used for the first time by employing the concept of fractional coordination numbers. They are used to interpolate between dispersion coefficients of atoms in different chemical environments. The method only requires adjustment of two global parameters for each density functional, is asymptotically exact for a gas of weakly interacting neutral atoms and easily allows the computation of atomic forces. It is assessed on standard benchmark sets for inter- and intra-molecular non-covalent interactions with a particular emphasis on a consistent description of light and heavy element systems. The mean absolute deviations for the S22 benchmark set [3] of non-covalent interactions for 11 standard density functionals decreases by 15-40 % compared to the previous (already accurate) DFT-D2 version [4]. Together with virtual-orbital dependent double-hybrid functionals, almost CCSD(T) accuracy for a wide range of inter- and intramolecular non-covalent interactions is obtained. Spectacular improvements are also found for peptide-folding models and all tested metallic systems already with standard GGA. In some detail, the choice of the necessary damping function in DFT-D type methods is investigated. We propose the revised method (termed DFT-D3) as a general tool for the fast computation of the dispersion energy in molecules and solids of any kind with DFT and related (low-cost) electronic structure methods for large systems.


[1] See e.g.: F. A. Gianturco and F. Paesani, J. Chem. Phys. 113, 3011 (2000).
X. Wu, M. C. Vargas, S. Nayak, V. Lotrich, and G. Scoles, J. Chem. Phys. 115, 8748 (2001).
M. Elstner, P. Hobza, T. Frauenheim, S. Suhai, and E. Kaxiras, J. Chem. Phys. 114, 5149 (2001).
Q. Wu and W. Yang, J. Chem. Phys. 116, 515 (2002). U. Zimmerli, M. Parrinello, and P. Koumoutsakos, J. Chem. Phys. 120, 2693 (2004). S. Grimme, J. Comput. Chem. 25, 1463 (2004).
[2] S. Grimme, J. Antony, S. Ehrlich, and H. Krieg, J. Chem. Phys., 132, 154104 (2010).
[3] P. Jurecka, J. Sponer, J. Cerny, and P. Hobza, Phys. Chem. Chem. Phys. 8, 1985 (2006).
[4] S. Grimme, J. Comput. Chem. 27, 1787 (2006).

Neuronal processing has a high energetic cost, all of which is supplied through brain vasculature. What are the design rules for this system? How is flow controlled by neuronal activity? How do neurons respond to failures in the vasculature? Theses questions will be addressed at the level of necortex in rat and mouse. An essential aspect of this work is the use of nonlinear optical tools to measure and perturb vasodynamics and automate the large-scale mapping of brain angioarchitecture.

Everybody knows that science, like poetry, is one step short from madness. Ettore Majorana was one of the greatest scientists of the 20th century and also one of the most tragic figures. In 1938 he disappeared in the sea. His body was never found. Before vanishing he had postulated that the neutrino, the mysterious particle invented by Wolfgang Pauli and christened by Enrico Fermi a few years before, was its own antiparticle.



A particle that is its own antiparticle reminds of a man who can't be distinguished from his own shadow. The neutrino, perhaps the tiniest bit of reality we can dream of, is still, more than 80 years after its conception to the world of ideas, as mysterious as Majorana himself.



Did Majorana die in the sea? Some scientists – some poets—prefer to think that he didn't and he lives still, retired from the World, in some remote and forgotten haven. Perhaps we will never know, but instead we may find whether the neutrino is its own antiparticle, by detecting neutrinoless double beta decay events. Those processes, whose lifetime is many orders of magnitude longer than that of the universe may hold the key to the question of the nature of the neutrino, and by extension help us to understand the cosmic asymmetry between matter and antimatter.