Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session P13: Time-Dependent Density Functional Theory |
Hide Abstracts |
Sponsoring Units: DCOMP Chair: E.K.U. Gross, Freie Universitat Berlin Room: Morial Convention Center 204 |
Wednesday, March 12, 2008 8:00AM - 8:12AM |
P13.00001: Energy and charge transfer in photoexcited molecules - A challenge for TDDFT Espen Sagvolden, Filipp Furche We study charge-transfer excitations and radiationless energy transfer between two chromophores (parts of a molecule which are individually excitable). These reactions have widespread chemical significance, particularly to the design of organic solar cell panels and molecular switches and to photosynthesis. Time-Dependent DFT (TDDFT) offers a very favorable relationship between accuracy and calculational cost in many cases. Calculations are performed for the (2-pyridone)$_2$-dimer which is experimentally well-characterized [1]. TDDFT is compared to experiment and competing methods such as Time-Dependent Hartree-Fock, CI singles, and coupled-cluster methods. \newline [1] A. M\"uller, F. Talbot, and S. Leutwyler, J. Chem. Phys. \textbf{112}, 2836 (2002). [Preview Abstract] |
Wednesday, March 12, 2008 8:12AM - 8:24AM |
P13.00002: Generator coordinates: a new road towards dynamics and excitations in DFT Klaus Capelle The generator-coordinate method is a flexible and powerful reformulation of the variational principle. Here we show that by introducing a generator coordinate in the Kohn-Sham equation of density-functional theory, excitation energies can be obtained from ground-state density functionals. Similarly, by introducing a generator coordinate in the equations of time-dependent DFT, memory effects can be built into any existing adiabatic exchange-correlation potential.(See J. Chem. Phys. 127, p. 124101 (2007) and J. Chem. Phys. 119, p. 1285 (2003).) [Preview Abstract] |
Wednesday, March 12, 2008 8:24AM - 8:36AM |
P13.00003: Time-Dependent Transport Phenomena: Bound-State Oscillations and Pumping Stefan Kurth, Elham Khosravi, Gianluca Stefanucci, Angel Rubio, Eberhard K.U. Gross We present a description of transport based on the time evolution of the non-interacting time-dependent Schr\"odinger equation and develop a numerical algorithm for the time propagation which is suited for implementation of time-dependent density functional theory (TDDFT). The algorithm is used to study time-dependent transport phenomena such as electron pumping, transients and bound state oscillations. It has been shown recently [Phys. Rev. B {\bf 75}, 195115 (2007)] that the presence of at least two bound states in the biased electrode-device-electrode system of non interacting electrons leads to persistent oscillations in the total current whose amplitude depends on the history of the applied voltage and on the initial state. In the case of electron pumps driven by time-periodic gate voltages, the amplitude of these oscillations decays slowly with time. TDDFT results will be compared to those obtained for non-interacting electrons. [Preview Abstract] |
Wednesday, March 12, 2008 8:36AM - 8:48AM |
P13.00004: Time-dependent V-representability on lattice systems Yonghui Li, Carsten A. Ullrich We study the mapping between time-dependent densities and potentials on small lattices. As discovered recently by Baer (arXiv:0704.1787), there exist well-behaved time-dependent density functions on lattices which cannot be constructed from any real potential. However, one finds that such densities can always be reproduced by complex potentials. We analyze the breakdown of time-dependent V-representability on lattices and show that it is related to problems with the continuity equation which ultimately arise from discretization of the momentum operator. This imposes fundamental restrictions on practical numerical applications of TDDFT. In the continuum limit, time-dependent V-representability is restored. [Preview Abstract] |
Wednesday, March 12, 2008 8:48AM - 9:00AM |
P13.00005: TDDFT in Phase-Space Arun Rajam, Christian Gaun, Neepa Maitra We explore the possibility of a density-functional theory in phase-space, where the basic variable is a phase-space density rather than the usual coordinate-space density. In this way information about the momentum distribution is directly captured, rather than being hidden in the form of the exchange-correlation functionals, which often complicates the functional, making it hard to approximate. We give examples to motivate this approach, and discuss initial stages in the development of the functionals. [Preview Abstract] |
Wednesday, March 12, 2008 9:00AM - 9:12AM |
P13.00006: Linear and Non-Linear Optical Response using Real-Time Time-Dependent Density Functional Theory Y. Takimoto, F.D. Vila, J.J. Rehr We present an approach for the calculation of the frequency- dependent response of nano-scale organic molecules for non-linear optical (NLO) devices. These calculations are performed using an efficient implementation of real-time, time-dependent density functional theory (RT-TDDFT) \footnote{Y. Takimoto, F. D. Vila, and J. J. Rehr, J. Chem. Phys. {\bf 127}, 154114 (2007)}, and an adaptation of the SIESTA electronic structure code. This method yields frequency dependent nonlinear optical properties of large organic molecules, which have been difficult to obtain with frequency domain calculations. Here we discuss the efficiency of the method and compare the results against frequency-domain TDDFT methods and with experiment. Solvent effects on the NLO properties of photonic molecules are also briefly discussed. [Preview Abstract] |
Wednesday, March 12, 2008 9:12AM - 9:24AM |
P13.00007: Time-dependent density-functional approach for exciton binding energies Volodymyr Turkowski, Carsten A. Ullrich We use TDDFT to study ultrafast electron dynamics and excitonic effects in insulators and semiconductors. Within a two-band approximation of the linearized semiconductor Bloch equations, we derive a TDDFT version of the Wannier equation for excitonic wave functions and binding energies. The TDDFT Wannier equation produces in principle the exact excitonic spectrum. However, this puts stringent requirements on the exchange-correlation (XC) kernel. We analyze various XC kernels that lead to bound excitonic states, and propose new model XC kernels designed to reproduce experimental exciton spectra. [Preview Abstract] |
Wednesday, March 12, 2008 9:24AM - 9:36AM |
P13.00008: Autoionizing Resonances in TDDFT Harshani Wijewardane, August Krueger, Gabriella Mullady, Neepa Maitra In an independent particle picture such as the Kohn-Sham system, bound states with an energy above one of the occupied orbital ionizations are truly bound. When interaction is accounted for, configuration coupling turns the bound state into an autoionizing resonance. In exact TDDFT, it is the exchange-correlation kernel that mixes the ionized and bound state, creating a Fano resonance profile. Although autoionization peaks arising from single excitations have been accurately captured with the available functional approximations, resonances arising from double excitations lying in the continuum are missing. By studying a simple model system, we uncover the features of the exact exchange-correlation kernel that are needed to capture the lifetimes and lineshapes of these resonances accurately. [Preview Abstract] |
Wednesday, March 12, 2008 9:36AM - 9:48AM |
P13.00009: Viscosity contribution to the impurity resistivity of metals by means of the current-density functional theory Vladimir U. Nazarov, Giovanni Vignale Within the time-dependent density functional theory formalism we relate the impurity resistivity $\rho$ of a metal to the friction coefficient $Q$ of the metal for the same impurity moving with the infinitesimally small velocity, i.e., $ \rho=n_i Q / n_e^2 \, (1), $ where $n_i$ and $n_e$ are the concentrations of the randomly distributed impurities and the valence electrons, respectively. While Eq.(1) occurs trivial within the single-particle theory with the scattering at the {\em statically} screened impurities, its general validity within the many-body theory with the {\em dynamical} exchange and correlation included presents a progress. We utilize results [1,2] on $Q$ of the electron liquid to put the electron-electron scattering contribution into the terms of the viscosity coefficients [3]. Calculations of the residual resistivity of aluminum as a function of the atomic number of the impurity are performed, improving the agreement with experiment compared to the single- particle theory [4]. \noindent [1].V. U. Nazarov, J. M. Pitarke, C. S. Kim, and Y. Takada, Phys. Rev. B {\bf 71}, 121106(R) (2005). \noindent [2].V. U. Nazarov, J. M. Pitarke, Y. Takada, G. Vignale, and Y.-C. Chang, Phys. Rev. B {\bf 76}, 205103 (2007). \noindent [3].G. Vignale, C. A. Ullrich, and S. Conti, Phys. Rev. Lett. {\bf 79}, 4878 (1997). \noindent [4].M. J. Puska and R. M. Nieminen, Phys. Rev. B {\bf 27}, 6121 (1983). [Preview Abstract] |
Wednesday, March 12, 2008 9:48AM - 10:00AM |
P13.00010: Adiabatic connection fluctuation dissipation theorem density functionals beyond the random phase approximation Filipp Furche The random phase approximation (RPA) is an increasingly popular starting point for the construction of improved correlation energy functionals. As opposed to semi-local approximations, RPA-based functionals do not suffer from Coulomb self-interaction and naturally include van der Waals interactions; the price is higher computational cost. To compete with traditional correlated wavefunction methods, it is necessary to go beyond the bare RPA. I will analyze successes and failures of recent attempts to do so [1,2], and outline promising future directions. \newline [1] Z. Yan, J. P. Perdew, and S. Kurth, \textit{Phys. Rev. B} \textbf{61} (2000), 16430. \newline [2] F. Furche and T. Van Voorhis, \textit{J. Chem. Phys.} \textbf{122} (2005), 164106. [Preview Abstract] |
Wednesday, March 12, 2008 10:00AM - 10:12AM |
P13.00011: New Perspectives on the Fundamental Theorem of Density Functional Theory Viraht Sahni, Xiao-Yin Pan The fundamental theorem of time-dependent/time-independent DFT due to Runge-Gross(RG)/Hohenberg-Kohn(HK) proves the bijectivity between the density $ \rho({\bf r} t)/ \rho({\bf r})$ and the Hamiltonian ${\hat H}(t)/{\hat H}$ to within a function $C(t)$/constant $C$, and wave function $\Psi(t) /\Psi$. (Implicit in the RG theorem is that the initial condition $\Psi(t_{0})$ is fixed.) As such in DFT the wave function is considered solely a functional of the density. Since the density is gauge invariant, the wave function as a functional of the density is also gauge invariant. However, it is well known that the Hamiltonian and wave function are gauge variant. There is, therefore, an inherent inconsistency in the RG/HK theorem. We resolve this inconsistency of the theorem via a unitary or equivalently a gauge transformation. As a consequence we generalize the theorem to external potentials that include the momentum operator and a curl-free vector potential operator. The RG/HK theorems each then constitute a special case of this generalization. [Preview Abstract] |
Wednesday, March 12, 2008 10:12AM - 10:24AM |
P13.00012: Photo-excited dynamics of $\mathrm{CH_{2}N_{2}}$; time-dependent density functional theory Hosik Lee, Yoshiyuki Miyamoto A highly reactive organic molecule carbene has been an important subject in organic chemistry in several decades. The carbene which is formulated by $\mathrm{R_{1}R_{2}C:}$ shows high yield and lesser or no side products during its reaction [1]. By using ultra-fast (sub-pico second) laser flash photolysis(LFP) technique to its precursor diazirine or diazomethane, the highly reactive short-living ($\sim$100 fs) carbene can be conveniently prepared and used for production. In this study, photo-excited dynamics of diazirine and diazomethane will be shown within the scheme of the first- principles time-dependent density functional calculations. With quite good agreements to experimental photo-excitation spectra, our preliminary calculation results show different phases of molecular motion which hardly is achieved with thermal effect. Temperature-induced kinetic effect in the phto-excited dynamics also is discussed. [Preview Abstract] |
Wednesday, March 12, 2008 10:24AM - 10:36AM |
P13.00013: Time dependent density functional study of enhanced field emission from carbon nanotubes Joseph Driscoll, Kalman Varga We have calculated the field emission current of carbon nanotubes in real-time and real-space using the Lagrange- function basis [1] combined with efficient time-propagating schemes. Experimental studies reported orders of magnitude increase of field emission current from Cesium deposited carbon nanotubes [2]. We have studied the increase of field emission current due to the deposition of different atoms (Cesium, Gold, Tungsten, etc.) on capped carbon nanotube tips. The theoretical results are in good agreement with the experimental findings. This work was supperted by NSF grant ECS 0622146. \newline [1] K. Varga, Z. Zhang, and S. T. Pantelides, Phys. Rev. Lett. 93, 176403 (2004). \newline [2] A. Wadhawan, R. E. Stallcup, and J. M. Perez, Appl. Phys. Lett., 78 108 (2001). [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700