A5085295722- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Molecular spectroscopy and chirality
- Advanced NMR Techniques and Applications
- Machine Learning in Materials Science
- X-ray Diffraction in Crystallography
- Distributed and Parallel Computing Systems
- Crystallography and molecular interactions
- Molecular Junctions and Nanostructures
- Photochemistry and Electron Transfer Studies
- Nonlinear Optical Materials Research
- Scientific Computing and Data Management
- Chemical Thermodynamics and Molecular Structure
- Cloud Computing and Resource Management
- Solid-state spectroscopy and crystallography
- Synthesis and Properties of Aromatic Compounds
- Mass Spectrometry Techniques and Applications
- Protein Structure and Dynamics
- Semiconductor materials and interfaces
- Photochromic and Fluorescence Chemistry
- Nonlinear Dynamics and Pattern Formation
- Molecular Spectroscopy and Structure
- Protein Interaction Studies and Fluorescence Analysis
- Inorganic and Organometallic Chemistry
- Advanced Data Storage Technologies
VSB - Technical University of Ostrava
2012-2024
Lundbeck Foundation
2007-2012
Aarhus University
2007-2012
Institute for Chemical and Physical Processes
2005-2008
KTH Royal Institute of Technology
2001-2006
National Research Council
2006
AlbaNova
2004
Comenius University Bratislava
2002
Linköping University
2001
Dalton is a powerful general-purpose program system for the study of molecular electronic structure at Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, Møller-Plesset, configuration-interaction, and coupled-cluster levels theory. Apart from total energy, wide variety properties may be calculated using these electronic-structure models. Molecular gradients Hessians are available geometry optimizations, dynamics, vibrational studies, whereas magnetic resonance optical...
Coupled cluster calculations can be carried out for large molecular systems via a set of that use small orbital fragments the full space. The error in correlation energy system is controlled by precision fragment calculations. determination spaces black box sense it does not depend on any user-provided fragmentation, rather are carefully selected and extended during calculation to give energies specified precision. computational method scales linearly with size massively parallel.
An experimental and theoretical study of the electronic structure copper phthalocyanine (CuPc) molecule is presented. We performed x-ray photoemission spectroscopy (XPS) photoabsorption [x-ray absorption near-edge (XANES)] gas phase experiments we compared results with self-consistent field, density functional theory (DFT), static-exchange calculations. In addition, ultraviolet photoelectron spectra (UPS) allowed disentangling several outer molecular orbitals. A detailed two highest occupied...
We present a thorough locality analysis of the divide-expand-consolidate amplitude equations for second-order Møller-Plesset perturbation theory and coupled cluster singles doubles (CCSD) model, which demonstrates that are local when expressed in terms set occupied unoccupied Hartree-Fock orbitals, such as least-change molecular basis. The thus shows CC calculation on large system may be carried out calculations small orbital fragments total system, where sizes fragment spaces determined...
It is demonstrated that a set of local orthonormal Hartree-Fock (HF) molecular orbitals can be obtained for both the occupied and virtual orbital spaces by minimizing powers variance using trust-region algorithm. For power exponent equal to one, Boys localization function obtained. increasing exponents, penalty delocalized increased smaller maximum spreads are encountered. Calculations on superbenzene, C(60), fragment titin protein show outlier may These disappear when larger than one. small...
We present a new orbital localization function based on the sum of fourth central moments orbitals. To improve locality, we impose power moment to act as penalty least local With two, occupied and virtual Hartree-Fock orbitals exhibit more rapid tail decay than from other schemes, making them suitable for use in correlation methods. propose that standard spread (the square root second moment) are used complementary measures characterize locality an orbital, irrespective scheme.
Previously, we have introduced the linear scaling coupled cluster (CC) divide-expand-consolidate (DEC) method, using an occupied space partitioning of standard correlation energy. In this article, show that energy may alternatively be expressed a virtual partitioning, and Lagrangian partitioned elements from both schemes. The partitionings leads to atomic site pair interaction energies which are term-wise invariant with respect orthogonal transformation among or orbitals. Evaluating local...
Divide-Expand-Consolidate (DEC) is a local correlation method where the inherent locality of electron problem used to express correlated calculation on large molecular system in terms small independent fragment calculations employing subsets HF orbitals. A crucial feature DEC scheme that sizes orbital spaces are determined black box manner during calculation. In this way it ensured energy has been predefined precision compared conventional present work we apply calculate as well density...
The trust region method has been applied to the minimization of localization functions, and it is shown that both local occupied virtual Hartree-Fock (HF) orbitals can be obtained. Because step sizes are size extensive in method, large steps may required when molecular systems. For an exponential parametrization function only small allowed, standard radius update therefore replaced by a scheme where direction determined using conservative estimate length from line search along obtained...
A linear-scaling implementation of Hartree-Fock and Kohn-Sham self-consistent field theories for the calculation frequency-dependent molecular response properties excitation energies is presented, based on a nonredundant exponential parametrization one-electron density matrix in atomic-orbital basis, avoiding use canonical orbitals. The equations are solved iteratively, by an subspace method equivalent to that molecular-orbital theory. Important features paired trial vectors (to preserve...
Density fitting is an important method for speeding up quantum-chemical calculations. Linear-scaling developments in Hartree-Fock and density-functional theories have highlighted the need linear-scaling density-fitting schemes. In this paper, we present a robust variational scheme that allows solving equations local metrics instead of traditional Coulomb metric, as required linear scaling. Results four-center two-electron integrals overlap attenuated Gaussian damped metric are presented,...
A linear-scaling implementation of Hartree-Fock and Kohn-Sham self-consistent field (SCF) theories is presented illustrated with applications to molecules consisting more than 1000 atoms. The diagonalization bottleneck traditional SCF methods avoided by carrying out a minimization the Roothaan-Hall (RH) energy function solving Newton equations using preconditioned conjugate-gradient (PCG) method. For rapid PCG convergence, Lowdin orthogonal atomic orbital basis used. resulting trust-region...
We present density-functional theory for time-dependent response functions up to and including cubic response. The working expressions are derived from an explicit exponential parametrization of the density operator Ehrenfest principle, alternatively, quasienergy ansatz. While retains adiabatic approximation, implying that time-dependency functional is obtained only implicitly-through time dependence itself rather than through form exchange-correlation functionals-it generalizes previous...
Recent advances in orbital localization algorithms are used to minimize the Pipek-Mezey function for both occupied and virtual Hartree-Fock orbitals. Virtual orbitals large molecular systems have previously not been considered literature. For this work, (PM) is implemented Mulliken a Löwdin population analysis. The results show that standard PM (using either or analyses) may yield local orbitals, although some only semilocal as compared state-of-the-art localized analysis shows improvement...
For large molecular systems conventional implementations of second order Møller–Plesset (MP2) theory encounter a scaling wall, both memory- and time-wise. We describe how this wall can be removed. present massively parallel algorithm for calculating MP2 energies densities using the divide–expand–consolidate scheme where calculation on system is divided into many small fragment calculations employing local orbital spaces. The resulting linear-scaling with size, exhibits near perfect...
We present a robust linear-scaling algorithm to compute the symmetric square-root or Lowdin decomposition of atomic-orbital overlap matrix. The method is based on Newton-Schulz iterations with new approach starting matrices. Calculations 12 chemically and structurally diverse molecules demonstrate efficiency reliability method. Furthermore, calculations show that linear scaling achieved.
We present a novel method for the optimization of Hartree-Fock and Kohn-Sham energies that does not suffer from flaws conventionally used two-step Roothaan-Hall (RH) with direct inversion in iterative subspace (DIIS) acceleration scheme, improving reliability while reducing its cost. The key to success is replacement two separate steps each RH/DIIS iteration by single concerted step fully exploits Hessian information available previous iterations. It trust-region based therefore design...
We demonstrate that the divide-expand-consolidate (DEC) scheme--which has previously been used to determine second-order Møller-Plesset (MP2) correlation energy--can be applied evaluate MP2 molecular gradient in a linear-scaling and embarrassingly parallel manner using set of local Hartree-Fock orbitals. All manipulations four-index quantities (describing electron effects) are carried out small orbital fragment spaces, whereas two-index treated for full system. The sizes spaces determined...
A new strategy is introduced for obtaining localized orthonormal Hartree–Fock (HF) orbitals where the underlying principle to minimize size of transformation matrix from atomic orbital basis HF optimized basis. The gives both occupied and virtual spaces. locality space similar one obtained using standard localization schemes. For space, schemes fail give local while a which has Löwdin orthonormalization Since most functions in sense that they have largest similarity with functions, thus...
Using a recently derived origin-invariant quadratic response approach combined with time-dependent density functional theory, four representative helicenes are shown to present very strong two-photon circular dichroism (TPCD) response, which makes them candidates for the first experimental observation of TPCD effect. The large is attributed unique combination chirality and electron delocalization. Comparison electronic absorption (TPA) shows that three effects exhibit complementary features...
Two-photon circular dichroism spectra calculated within an origin-invariant density functional theory approximation in the absorption region where lowest electronic excited states appear are presented for all 19 essential amino acids gas phase. A comparison of intensities and characteristic features is made with corresponding two-photon one-photon each species. Also, contributions electric dipole, magnetic quadrupole transitions to rotational strengths analyzed some detail. The remarkable...
Three-photon absorption probabilities δ3PA have been calculated through application of a recently derived method for cubic response functions within density functional theory (DFT). Calculations are compared with Hartree–Fock (HF) and coupled cluster hierarchy models in benchmarking procedure. Except cases having intermediate states near resonance, is demonstrated to be sufficient agreement the highly correlated methods order qualify predictions δ3PA. For larger systems addressed, set...