A5017591549- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Advanced NMR Techniques and Applications
- Machine Learning in Materials Science
- X-ray Diffraction in Crystallography
- Crystallography and molecular interactions
- Molecular Junctions and Nanostructures
- Molecular spectroscopy and chirality
- Theoretical and Computational Physics
- Photochromic and Fluorescence Chemistry
- Cold Atom Physics and Bose-Einstein Condensates
- 3D Modeling in Geospatial Applications
- Surface Chemistry and Catalysis
- DNA and Nucleic Acid Chemistry
- Random Matrices and Applications
- Magnetism in coordination complexes
- Experimental Learning in Engineering
- Quantum Computing Algorithms and Architecture
- Magnetic and transport properties of perovskites and related materials
- Nuclear physics research studies
- Chemical Reaction Mechanisms
- Enzyme Structure and Function
- Quantum many-body systems
- Photoreceptor and optogenetics research
- Thermal and Kinetic Analysis
Norwegian University of Science and Technology
2009-2025
John Wiley & Sons (United States)
2021
University of Oslo
2017
Aarhus University
2012-2013
Lundbeck Foundation
2009-2012
Middle East Technical University
2009
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...
The eT program is an open source electronic structure package with emphasis on coupled cluster and multilevel methods. It includes efficient spin adapted implementations of ground excited singlet states, as well equation motion oscillator strengths, for CCS, CC2, CCSD, CC3. Furthermore, provides unique capabilities such Hartree–Fock real-time propagation CCS CC3 strengths. With a code based Cholesky decomposition algorithm the repulsion integrals, has similar advantages codes using density...
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...
We introduce an approach to describe fractional charging of molecules interacting non-covalently with their environment. The formalism is based on dividing the full orbital space into orbitals localized molecule and This enables a separation electronic Hamiltonian terms referencing only molecule, environment, or interaction terms. are divided particle-conserving interactions particle-non-conserving (particle-breaking) interactions. dominant may be included using standard embedding schemes....
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...
In this article, we present a black-box approach for the selection of orbital spaces when computing core excitation energies in multilevel coupled cluster (MLCC) framework. Information available from lower level theory is used to generate correlated natural transition orbitals (CNTOs) high-level calculation by including both singles and doubles information construction orbitals. The inclusion essential obtain set that all contain physical information, contrast where only small subset virtual...
We introduce a density-based multilevel Hartree–Fock (HF) method where the electronic density is optimized in given region of molecule (the active region). Active molecular orbitals (MOs) are generated by decomposition starting guess atomic orbital (AO) density, whereas inactive MOs (which constitute remainder density) never or referenced. The MO formulation allows for significant dimension reduction transforming from AO basis to basis. All interactions between and regions retained, an...
A multiresolution procedure to construct potential energy surfaces (PESs) for use in vibrational structure calculations is developed the framework of adaptive density-guided approach. The implementation method allows construction hybrid PESs with different mode-coupling terms calculated a variety combinations electronic methods and basis sets. Furthermore, that incorporate contributions corrections energy, such as infinite set extrapolation core correlation effects. full account given...
In this work we present the particle-breaking Hartree–Fock (PBHF) model which is a mean-field approach to open molecular systems. The interaction of system with environment parametrized through term in Hamiltonian. PBHF wave function constructed an exponential unitary transformation Slater determinant given number electrons. We consider only closed-shell formalism. parametrization results linear combination determinants different numbers electrons, i.e., not eigenfunction operator. As...
We recently introduced the particle-breaking restricted Hartree–Fock (PBRHF) model, a mean-field approach to address fractional charging of molecules when they interact with an electronic environment. In this paper, we present extension model referred as unrestricted (PBUHF). The formulation contains odd-electron states necessary for realistic description charging. Within PBUHF parametrization, use two-body operators yield convenient operator transformations. However, can change only...
In the previously introduced multilevel Hartree–Fock (HF) model, electronic density is optimised in a given region of molecular system. The approach based on generating an active occupied and virtual space by decomposing start guess for entire this work, diagonalisation implementation Roothaan–Hall (RH) with direct inversion iterative subspace (DIIS) quasi-Newton minimisation procedure using augmented RH (ARH) are described accelerating convergence HF model. equations derived to be...
To handle energetic materials safely, it is important to have knowledge about their sensitivity. Density functional theory (DFT) has proven a valuable tool in the study of materials, and current work, DFT employed thermal unimolecular decomposition 2,4,6-trinitrophenol (picric acid, PA), 3-methyl-2,4,6-trinitrophenol (methyl picric mPA), 3,5-dimethyl-2,4,6-trinitrophenol (dimethyl dmPA). These compounds similar molecular structures, but according literature, mPA far less sensitive impact...
Abstract Using the three‐level energy optimization procedure combined with a refined version of least‐change strategy for orbitals—where an explicit localization is performed at valence basis level—it shown how to more efficiently determine set local Hartree–Fock orbitals. Further, core–valence separation occupied orbital space introduced. Numerical results comparing localized orbitals and canonical molecular as starting guesses full are presented. The show that may be small computational...
When a set of orthogonal orbitals is localised using transformations, the orbital metric conserved as unit matrix during localisation. In this paper we describe how non-orthogonal may be by requiring that conserved. particular, demonstrate exponential mappings used to parametrise transformations such Using parametrisation, localisation becomes generalisation for orbitals, where conservation replaced non-unit metric. As result, standard functions and optimisation algorithms have been...
We present a trust-region optimization of the Edmiston-Ruedenberg orbital localization function. The approach is used to localize both occupied and virtual orbitals first demonstration general using In approach, sum self-repulsion energies maximized obtain localized orbitals. Cholesky decomposition reduces cost transforming electron repulsion integrals, overall scaling our implementation O(N4). performed with all quantities in molecular basis, often less expensive than corresponding...
Orbital localization of occupied and virtual Hartree-Fock orbitals generated from basis sets augmented with diffuse functions is performed using the Pipek-Mezey, Boys, powers second central moment, fourth moment localizations. The locality obtained orbital are presented in terms spreads. results show that both local may be when localizations, while Pipek-Mezey Boys localizations fail to produce orbitals. exhibits a similar for non-augmented sets.
It is well known that near-linear dependencies in the atomic orbital (AO) basis will impede electronic-structure calculations since inverse AO overlap matrix be ill-defined. However, small eigenvalues also impact locality of virtual density matrix. The relevant for developing efficient local approaches theory, and recent literature shows orthogonal molecular orbitals (MOs) are not optimal exploiting locality. As size molecules treated increasing high-quality sets used, problem becoming more...
In this article we use MP2 and CCSD(T) calculations for the A24 S66 data sets to explore how midbond functions can be used generate cost effective counterpoise corrected supramolecular interaction energies of noncovalent complexes. We set show that primary role is not approach complete basis limit, but rather ensure a balanced description molecules region (unrelated superposition error). The need balance consequence using atom centered sets. error will disappear, reaching limit feasible...
Abstract This paper presents a report from an early phase of the project Mathematics as Thinking Tool. The primary goal this is to increase engineering students’ perception relevance mathematics by developing close connection between and subjects, develop approach driven learning goals study programme rather than in specific subjects. We will present examples electrical chemistry show how may play along with other fields order deep conceptual understanding. Some preliminary results student...
Abstract In this article, we use two extensively studied systems, a retinal model system and azobenzene, to explore the of coupled cluster models for describing ground singlet excited state potential energy surfaces photoswitchable systems. While not being suitable nuclear dynamics photoisomerization, have useful attributes, such as inclusion dynamical correlation, their black box nature, systematic improvement offered by truncation level. Results systems show that when triple excitations...