Methods for Assessing Technology Transfer - An Overview

As triple-helix like research funding is growing in popularity, the need for evaluating the success of such programs is growing. During the last 30 years, a number of attempts have been made to assess whether certain technology funding has been successful or not. The purpose of this paper is to present an overview of these attempts as well as suggest that we must look beyond simple valuemeters as patent creation rate in order to fully understand the process of technology transfer.technology transfer, assessment, patent, innovation management

Optical excitations of Si by time-dependent density-functional theory based on the exact-exchange Kohn-Sham band structure

We calculate the imaginary part of the frequency-dependent dielectric function of bulk silicon by applying time-dependent density-functional theory based on the exact-exchange (EXX) Kohn-Sham (KS) band structure and the adiabatic local-density approximation (ALDA) kernel. The position of the E2 absorption peak calculated with the EXX band structure at the independent-particle level is in excellent agreement with experiments, which demonstrates the good quality of EXX `KS quasiparticles'. The excitonic E1 peak that is missing at the independent-particle level remains absent if two-particle interaction effects are taken into account within the time-dependent LDA, demonstrating the incapability of the ALDA kernel to describe excitonic effects.Comment: 6 pages, 2 figures; contribution to "DFT 2001", Sep. 10-14, San Lorenzo de El Escorial, Spain; to be published in Int. J. Quantum. Che

Double-Pole Approximation in Time-Dependent Density Functional Theory

A simple approximate solution to the linear response equations of time-dependent density functional theory (TDDFT) is given. This extends the single-pole approximation (SPA) to two strongly-coupled poles. The analysis provides both an illustration of how TDDFT works when strong exchange-correlation effects are present and insight into such corrections. For example, interaction can cause a transition to vanish entirely from the optical spectrum.Comment: 7 pages, 11 figure

Local exact exchange potentials within the all-electron FLAPW method and a comparison with pseudopotential results

We present a general numerical approach to construct local Kohn-Sham potentials from orbital-dependent functionals within the all-electron full-potential linearized augmented-plane-wave (FLAPW) method, in which core and valence electrons are treated on an equal footing. As a practical example, we present a treatment of the orbital-dependent exact-exchange (EXX) energy and potential. A formulation in terms of a mixed product basis, which is constructed from products of LAPW basis functions, enables a solution of the optimized-effective-potential (OEP) equation with standard numerical algebraic tools and without shape approximations for the resulting potential. We find that the mixed product and LAPW basis sets must be properly balanced to obtain smooth and converged EXX potentials without spurious oscillations. The construction and convergence of the exchange potential is analyzed in detail for diamond. Our all-electron results for C, Si, SiC, Ge, GaAs semiconductors as well as Ne and Ar noble-gas solids are in very favorable agreement with plane-wave pseudopotential calculations. This confirms the adequacy of the pseudopotential approximation in the context of the EXX-OEP formalism and clarifies a previous contradiction between FLAPW and pseudopotential results.Comment: 12 pages, 7 figures, 5 table

Precise response functions in all-electron methods: Application to the optimized-effective-potential approach

The optimized-effective-potential (OEP) method is a special technique to construct local Kohn-Sham potentials from general orbital-dependent energy functionals. In a recent publication [M. Betzinger, C. Friedrich, S. Bl\"ugel, A. G\"orling, Phys. Rev. B 83, 045105 (2011)] we showed that uneconomically large basis sets were required to obtain a smooth local potential without spurious oscillations within the full-potential linearized augmented-plane-wave method (FLAPW). This could be attributed to the slow convergence behavior of the density response function. In this paper, we derive an incomplete-basis-set correction for the response, which consists of two terms: (1) a correction that is formally similar to the Pulay correction in atomic-force calculations and (2) a numerically more important basis response term originating from the potential dependence of the basis functions. The basis response term is constructed from the solutions of radial Sternheimer equations in the muffin-tin spheres. With these corrections the local potential converges at much smaller basis sets, at much fewer states, and its construction becomes numerically very stable. We analyze the improvements for rock-salt ScN and report results for BN, AlN, and GaN, as well as the perovskites CaTiO3, SrTiO3, and BaTiO3. The incomplete-basis-set correction can be applied to other electronic-structure methods with potential-dependent basis sets and opens the perspective to investigate a broad spectrum of problems in theoretical solid-state physics that involve response functions.Comment: 17 pages, 7 figures, 3 table

Accurate Adiabatic Connection Curve Beyond the Physical Interaction Strength

The adiabatic connection curve of density functional theory (DFT) is accurately calculated beyond the physical interaction strength for Hooke's atom, two interacting electrons in a harmonic well potential. Extrapolation of the accurate curve to the infinite coupling limit agrees well with the strictly correlated electron (SCE) hypothesis but the approach to this limit is more complex. The interaction strength interpolation is shown to be a good, but not perfect, fit to the adiabatic curve. Arguments about the locality of functionals and convexity of the adiabatic connection curve are examined in this regime.Comment: 7 pages, 5 figure

Exchange and Correlation Kernels at the Resonance Frequency -- Implications for Excitation Energies in Density-Functional Theory

Specific matrix elements of exchange and correlation kernels in time-dependent density-functional theory are computed. The knowledge of these matrix elements not only constraints approximate time-dependent functionals, but also allows to link different practical approaches to excited states, either based on density-functional theory, or on many-body perturbation theory, despite the approximations that have been performed to derive them.Comment: Submitted to Phys. Rev. Lett. (February 4, 1999). Other related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Density-to-potential map in time-independent excited-state density-functional theory

In light of the recent work by Sahni et al., Harbola, and Gaudoin and Burke, the question of mapping from an excited-state density of a many-electron interacting system to the potential of the related non-interacting system is analyzed. To do so, we investigate the Levy-Nagy criterion quantitatively for several excited-states. Our work indicates that Levy-Nagy criterion may fix the density to potential map uniquely

Exact-Exchange Kohn-Sham formalism applied to one-dimensional periodic electronic systems

The Exact-Exchange (EXX) Kohn-Sham formalism, which treats exchange interactions exactly within density-functional theory, is applied to one-dimensional periodic systems. The underlying implementation does not rely on specific symmetries of the considered system and can be applied to any kind of periodic structure in one to three dimensions. As a test system, $trans$-polyacetylene, both in form of an isolated chain and in the bulk geometry has been investigated. Within the EXX scheme, bandstructures and independent particle response functions are calculated and compared to experimental data as well as to data calculated by several other methods. Compared to results from the local-density approximation, the EXX method leads to an increased value for the band gap, in line with similar observations for three-dimensional semiconductors. An inclusion of correlation potentials within the local density approximation or generalized gradient approximations leads to only negligible effects in the bandstructure. The EXX band gaps are in good agreement with experimental data for bulk $trans$-polyacetylene. Packing effects of the chains in bulk $trans$-polyacetylene are found to lower the band gap by about 0.5 eV