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186 results on '"Harding, Michael E."'

1. Approaching the basis-set limit of the dRPA correlation energy with explicitly correlated and Projector Augmented-wave methods

Author

Humer, Moritz, Harding, Michael E., Schlipf, Martin, Taheridehkordi, Amir, Sukurma, Zoran, Klopper, Wim, and Kresse, Georg

Subjects
Physics - Chemical Physics, Physics - Computational Physics
Abstract

The direct random-phase approximation (dRPA) is used to calculate and compare atomization energies for the HEAT set and 10 selected molecules of the G2-1 set using both plane waves and Gaussian-type orbitals. We describe detailed procedures to obtain highly accurate and well converged results for the projector augmented-wave (PAW) method as implemented in the Vienna Ab-initio Simulation Package (VASP) as well as the explicitly correlated dRPA-F12 method as implemented in the TURBOMOLE package. The two approaches agree within chemical accuracy (1 kcal/mol) for the atomization energies of all considered molecules, both for the exact exchange as well as for the dRPA. The root mean-square deviation is 0.41 kcal/mol for the exact exchange (evaluated using density functional theory orbitals) and 0.33 kcal/mol for exact exchange plus the random-phase approximation., Comment: 16 pages, 2 figures

Published
2022
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2. Determination of accurate rest frequencies and hyperfine structure parameters of cyanobutadiyne, HC$_5$N

Author

Giesen, Thomas F., Harding, Michael E., Gauss, Jürgen, Grabow, Jens-Uwe, and Müller, Holger S. P.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Astrophysics of Galaxies, Physics - Atomic and Molecular Clusters, Physics - Chemical Physics
Abstract

Very accurate transition frequencies of HC$_5$N were determined between 5.3 and 21.4 GHz with a Fourier transform microwave spectrometer. The molecules were generated by passing a mixture of HC$_3$N and C$_2$H$_2$ highly diluted in neon through a discharge valve followed by supersonic expansion into the Fabry-Perot cavity of the spectrometer. The accuracies of the data permitted us to improve the experimental $^{14}$N nuclear quadrupole coupling parameter considerably and the first experimental determination of the $^{14}$N nuclear spin-rotation parameter. The transition frequencies are also well suited to determine in astronomical observations the local speed of rest velocities in molecular clouds with high fidelity. The same setup was used to study HC$_7$N, albeit with modest improvement of the experimental $^{14}$N nuclear quadrupole coupling parameter. Quantum chemical calculations were carried out to determine $^{14}$N nuclear quadrupole and spin-rotation coupling parameters of HC$_5$N, HC$_7$N, and related molecules. These calculations included evaluation of vibrational and relativistic corrections to the non-relativistic equilibrium quadrupole coupling parameters; their considerations improved the agreement between calculated and experimental values substantially., Comment: 9 pages; J. Mol. Spectrosc., accepted

Published
2020
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3. Precision frequency-comb terahertz spectroscopy on pure quantum states of a single molecular ion

Author

Chou, Chin-wen, Collopy, Alejandra L., Kurz, Christoph, Lin, Yiheng, Harding, Michael E., Plessow, Philipp N., Fortier, Tara, Diddams, Scott, Leibfried, Dietrich, and Leibrandt, David. R.

Subjects
Physics - Atomic Physics, Astrophysics - Instrumentation and Methods for Astrophysics, Quantum Physics
Abstract

Spectroscopy is a powerful tool for studying molecules and is commonly performed on large thermal molecular ensembles that are perturbed by motional shifts and interactions with the environment and one another, resulting in convoluted spectra and limited resolution. Here, we use generally applicable quantum-logic techniques to prepare a trapped molecular ion in a single quantum state, drive terahertz rotational transitions with an optical frequency comb, and read out the final state non-destructively, leaving the molecule ready for further manipulation. We resolve rotational transitions to 11 significant digits and derive the rotational constant of CaH+ to be B_R = 142501777.9(1.7) kHz. Our approach suits a wide range of molecular ions, including polyatomics and species relevant for tests of fundamental physics, chemistry, and astrophysics., Comment: 25 pages, 4 figures, 6 tables

Published
2019
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5. TURBOMOLE: Modular program suite for ab initio quantum-chemical and condensed-matter simulations

Author

Balasubramani, Sree Ganesh, Chen, Guo P, Coriani, Sonia, Diedenhofen, Michael, Frank, Marius S, Franzke, Yannick J, Furche, Filipp, Grotjahn, Robin, Harding, Michael E, Hättig, Christof, Hellweg, Arnim, Helmich-Paris, Benjamin, Holzer, Christof, Huniar, Uwe, Kaupp, Martin, Khah, Alireza Marefat, Khani, Sarah Karbalaei, Müller, Thomas, Mack, Fabian, Nguyen, Brian D, Parker, Shane M, Perlt, Eva, Rappoport, Dmitrij, Reiter, Kevin, Roy, Saswata, Rückert, Matthias, Schmitz, Gunnar, Sierka, Marek, Tapavicza, Enrico, Tew, David P, van Wüllen, Christoph, Voora, Vamsee K, Weigend, Florian, Wodyński, Artur, and Yu, Jason M

Subjects
Physical Sciences, Chemical Sciences, Engineering, Chemical Physics
Abstract

TURBOMOLE is a collaborative, multi-national software development project aiming to provide highly efficient and stable computational tools for quantum chemical simulations of molecules, clusters, periodic systems, and solutions. The TURBOMOLE software suite is optimized for widely available, inexpensive, and resource-efficient hardware such as multi-core workstations and small computer clusters. TURBOMOLE specializes in electronic structure methods with outstanding accuracy-cost ratio, such as density functional theory including local hybrids and the random phase approximation (RPA), GW-Bethe-Salpeter methods, second-order Møller-Plesset theory, and explicitly correlated coupled-cluster methods. TURBOMOLE is based on Gaussian basis sets and has been pivotal for the development of many fast and low-scaling algorithms in the past three decades, such as integral-direct methods, fast multipole methods, the resolution-of-the-identity approximation, imaginary frequency integration, Laplace transform, and pair natural orbital methods. This review focuses on recent additions to TURBOMOLE's functionality, including excited-state methods, RPA and Green's function methods, relativistic approaches, high-order molecular properties, solvation effects, and periodic systems. A variety of illustrative applications along with accuracy and timing data are discussed. Moreover, available interfaces to users as well as other software are summarized. TURBOMOLE's current licensing, distribution, and support model are discussed, and an overview of TURBOMOLE's development workflow is provided. Challenges such as communication and outreach, software infrastructure, and funding are highlighted.

Published
2020

14. The first microsolvation step for furans: New experiments and benchmarking strategies

Author

Gottschalk, Hannes C., primary, Poblotzki, Anja, additional, Fatima, Mariyam, additional, Obenchain, Daniel A., additional, Pérez, Cristóbal, additional, Antony, Jens, additional, Auer, Alexander A., additional, Baptista, Leonardo, additional, Benoit, David M., additional, Bistoni, Giovanni, additional, Bohle, Fabian, additional, Dahmani, Rahma, additional, Firaha, Dzmitry, additional, Grimme, Stefan, additional, Hansen, Andreas, additional, Harding, Michael E., additional, Hochlaf, Majdi, additional, Holzer, Christof, additional, Jansen, Georg, additional, Klopper, Wim, additional, Kopp, Wassja A., additional, Krasowska, Małgorzata, additional, Kröger, Leif C., additional, Leonhard, Kai, additional, Mogren Al-Mogren, Muneerah, additional, Mouhib, Halima, additional, Neese, Frank, additional, Pereira, Max N., additional, Prakash, Muthuramalingam, additional, Ulusoy, Inga S., additional, Mata, Ricardo A., additional, Suhm, Martin A., additional, and Schnell, Melanie, additional

Published
2020
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22. The furan microsolvation blind challenge for quantum chemical methods: First steps

Author

Gottschalk, Hannes C., primary, Poblotzki, Anja, additional, Suhm, Martin A., additional, Al-Mogren, Muneerah M., additional, Antony, Jens, additional, Auer, Alexander A., additional, Baptista, Leonardo, additional, Benoit, David M., additional, Bistoni, Giovanni, additional, Bohle, Fabian, additional, Dahmani, Rahma, additional, Firaha, Dzmitry, additional, Grimme, Stefan, additional, Hansen, Andreas, additional, Harding, Michael E., additional, Hochlaf, Majdi, additional, Holzer, Christof, additional, Jansen, Georg, additional, Klopper, Wim, additional, Kopp, Wassja A., additional, Kröger, Leif C., additional, Leonhard, Kai, additional, Mouhib, Halima, additional, Neese, Frank, additional, Pereira, Max N., additional, Ulusoy, Inga S., additional, Wuttke, Axel, additional, and Mata, Ricardo A., additional

Published
2018
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23. Correlation of the structural information obtained for europium-chelate ensembles from gas-phase photoluminescence and ion-mobility spectroscopy with density-functional computations and ligand-field theory

Author

Greisch, Jean-François, primary, Chmela, Jiří, additional, Harding, Michael E., additional, Wunderlich, Dirk, additional, Schäfer, Bernhard, additional, Ruben, Mario, additional, Klopper, Wim, additional, Schooss, Detlef, additional, and Kappes, Manfred M., additional

Published
2017
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26. A litmus test for the balanced description of dispersion interactions and coordination chemistry of lanthanoids.

Author

Quesada, Juana Vázquez, Chmela, Jiří, Greisch, Jean-François, Klopper, Wim, and Harding, Michael E.

Abstract

The influence of long-range interactions on the structure of complexes of Eu(III) with four 9-hydroxy-phenalen-1-one ligands (HPLN) and one alkaline earth metal dication [Eu(PLN)4AE]+ (AE: Mg, Ca, Sr, and Ba) is analyzed. Through the [Eu(PLN)4Ca]+ complex, which is a charged complex with two metals—one of them a lanthanoid—and with four relatively fluxional π-ligands, the difficulties of describing such systems are identified. The inclusion of the D3(BJ) or D4 corrections to different density functionals introduces significant changes in the structure, which are shown to stem from the interaction between pairs of PLN ligands. This interaction is studied further with a variety of density functionals, wave-function based methods, and by means of the random phase approximation. By comparing the computed results with those from experimental evidence of gas-phase photoluminescence and ion mobility measurements it is concluded that the inclusion of dispersion corrections does not always yield structures that are in agreement with the experimental findings. [ABSTRACT FROM AUTHOR]

Published
2022
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28. A highly flexible molecule: The peculiar case of ethynyl isothiocyanate HCCNCS.

Author

Wenhao Sun, Davis, Rebecca L., Thorwirth, Sven, Harding, Michael E., and van Wijngaarden, Jennifer

Subjects
ETHYNYL compounds, SPIN excitations, POTENTIAL energy, ELECTRONIC excitation, FOURIER transform spectroscopy
Abstract

The rotational spectrum of the parent isotopic species of HCCNCS, along with those of three 13 C singly substituted variants and one 34 S minor isotopologue, has been observed with high resolution using Fourier transform microwave spectroscopy from 4 to 26 GHz. Based on the observed spectral pattern and assignment of the 14N nuclear quadrupole hyperfine structure, the geometry of HCCNCS is effectively linear, which is further supported by the observation of ϱ-type doubling for rotational transitions in an excited bending state of the parent HCCNCS. The experimental observations are supported by high level quantum chemical calculations using the coupled-cluster singles and doubles model augmented by a perturbative correction for triple excitations, CCSD(T), level of theory that reveal an extremely shallow potential energy well along the CNC bending angle with a surprising basis set dependence. [ABSTRACT FROM AUTHOR]

Published
2018
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36. High-Resolution Spectroscopy of C3 around 3 μm

Author

Krieg, Jürgen, primary, Lutter, Volker, additional, Endres, Christian P., additional, Keppeler, Imke H., additional, Jensen, Per, additional, Harding, Michael E., additional, Vázquez, Juana, additional, Schlemmer, Stephan, additional, Giesen, Thomas F., additional, and Thorwirth, Sven, additional

Published
2013
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