The goal of research in our group is to develop new electronic structure methods and to apply them to chemistry.

Most successful theoretical models in chemistry share the following characteristics: (i) They provide useful accuracy at a reasonable price, (ii) they are robust, i.e., applicable to a variety of different systems and properties. We use these criteria to select and develop electronic structure methods. This includes fundamentally new directions, such as the random phase approximation for correlation [15,19] and beyond [8], as well as improvements or extensions of established methods [7,18]. We are specifically interested in methods showing promise for excited states and large systems.

An central task of applied electronic structure theory is the development of efficient algorithms for molecular property calculations. Using rigorous approximation methods we aim to control the explosion of computational cost for larger systems which severely restricts the use of traditional electronic structure methods. For example, excited state structures and emission energies of molecules with well over 100 atoms can now be computed by virtue of our efficient analytical excited state gradient implementation [2,7,9] based on time-dependent density functional theory (TDDFT). Other properties of interest include (non-)linear optical properties, e.g. polarizabilities, Raman intensities [13], chiroptical properties such as circular dichroism (CD), vibrational spectra, and non-adiabatic couplings [18]. These developments are made available through the TURBOMOLE quantum chemistry package. TURBOMOLE is a highly efficient code specifically designed for small and medium size computing facilities; typical calculations take 1-3 days on a Linux workstation.

The first step after successful development and implementation of a new method are benchmarks, e. g., for excited state properties [5] or transition metal compounds [10]. We enjoy a number of strong collaborations with experimental groups within and outside UCI. Often, our methods allow applications to systems or properties that were not accessible before. Systems studied by us include (chiral) fullerenes [3,4], see Figure 1, structures and properties of gold clusters [1,11,14], cephams [12], and lanthanide dinitrogen and nitrosyl complexes [17,20].

Figure 1. The absolute configuration of the chiral fullerene D2-C84 was established by comparison of TDDFT calculations (red line) and experiment (blue line) [3]. Previous semi-empirical CNDO/S calculations (green line) were not accurate enough, while correlated wavefunction methods are still prohibitively expensive.

References:

[1] The structures of small gold cluster anions as determined by a combination of ion mobility measurements and density functional calculations. F. Furche, R. Ahlrichs, P. Weis, C. Jacob, S. Gilb, T. Bierweiler, and M. M. Kappes, J. Chem. Phys. 117 (2002), 6982.

[2] Adiabatic time-dependent density functional methods for excited state properties. F. Furche and R. Ahlrichs, J. Chem. Phys. 117 (2002), 7433; J. Chem. Phys. 121 (2004), 12772 (E).

[3] Absolute configuration of D2-symmetric fullerene C84. F. Furche and R. Ahlrichs, J. Am. Chem. Soc. 124 (2002), 3804.

[4] Photoelectron spectroscopy of C84 dianions. O. T. Ehrler, J. M. Weber, F. Furche, and M. M. Kappes, Phys. Rev. Lett. 384 (2003), 103.

[5] Photoinduced intramolecular charge transfer in 4-(dimethyl)aminobenzonitrile — a theoretical perspective. D. Rappoport and F. Furche, J. Am. Chem. Soc. 126 (2004), 1277.

[6] Towards a practical pair-density functional theory for many-electron systems. F. Furche, Phys. Rev. A 70 (2004), 022514.

[7] Analytical time-dependent density functional derivative methods within the RI-J approximation, an approach to excited states of large molecules. D. Rappoport and F. Furche, J. Chem. Phys. 122 (2005), 064105.

[8] Fluctuation-dissipation theorem density functional theory. F. Furche and T. Van Voorhis, J. Chem. Phys. 122 (2005), 164106.

[9] Excited states and Photochemistry. D. Rappoport and F. Furche, In Time-dependent density functional theory, edited by M. Marques, C. A. Ullrich, F. Nogueira, A. Rubio, K. Burke, and E. K. U. Gross, Springer, Berlin, 2006, p. 337.

[10] The performance of semi-local and hybrid functionals in 3d transition metal chemistry. F. Furche and J. P. Perdew, J. Chem. Phys. 122 (2006), 044103.

[11] Au34-: A chiral gold cluster? A. Lechtken, D. Schooss, J. Stairs, M. N. Blom, F. Furche, B. von Issendorf, and M. M. Kappes, Angew. Chem. Int. Ed. 46 (2007), 2944, Angew. Chem. 119 (2007), 3002.

[12] Circular dichroism and conformational dynamics of cephams and their carba- and oxaanalogues. J. Frelek, P. Kowalska, M. Masnyk, A. Kazimierski, A. Korda, M. Woznica, M. Chmielewski, and F. Furche, Chem. Eur. J. 13 (2007), 6732.

[13] Lagrangian approach to molecular vibrational Raman intensities using time-dependent hybrid density functional theory. D. Rappoport and F. Furche, J. Chem. Phys. 126 (2007), 201104.

[14] 2D-3D transition of gold cluster anions resolved. M. P. Johansson, A. Lechtken, D. Schooss, M. M. Kappes, and F. Furche, Phys. Rev. A 77 (2008), 053202, also published in Virtual Journal of Nanoscale Science & Technology 17 (2008).

[15] Developing the random phase approximation into a practical post-Kohn-Sham correlation model. F. Furche, J. Chem. Phys. 129 (2008), 114105.

[16] Förster energy transfer and Davydov splittings in time-dependent density functional theory: Lessons from 2-pyridone dimer. E. Sagvolden, F. Furche, and A. Köhn, J. Chem. Theor. Comput. 5 (2009), 873.

[17] Isolation of dysprosium and yttrium complexes of a three-electron reduction product in the activation of dinitrogen, the (N2)3- radical. W. J. Evans, M. Fang, G. Zucchi, F. Furche, J. W. Ziller, R. M. Hoekstra, and J. I. Zink, J. Am. Chem. Soc. 131 (2009), 11195.

[18] First-order nonadiabatic couplings from time-dependent hybrid density functional response theory: Consistent formalism, implementation, and performance. R. Send and F. Furche, J. Chem. Phys. 132 (2010), 044107.

[19] Fast computation of molecular random phase approximation correlation energies using resolution of the identity and imaginary frequency integration. H. Eshuis, J. Yarkoni, and F. Furche, J. Chem. Phys. 132 (2010), 234114.

[20] Isolation of a radical dianion of nitrogen oxide (NO)2-. W. J. Evans, M. Fang, J. E. Bates, F. Furche, J. W. Ziller, M. D. Kiesz, and J. I. Zink, Nature Chem. 2 (2010), 644.

[21] Property-optimized Gaussian basis sets for molecular response calculations. D. Rappoport and F. Furche, J. Chem. Phys. 133 (2010), 134105.