What can clusters tell us about the bulk?

Kirchner, Barbara; Spickermann, Christian; Lehmann, Sebastian B. C.; Perlt, Eva; Langner, Johanna; Domaros, Michael von; Reuther, Patricia; Uhlig, F.; Kohagen, Miriam; Brüssel, Marc

doi:10.1016/j.cpc.2011.03.011

Cited by 48 publications

(51 citation statements)

References 47 publications

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“…For mixtures, experimental data over the whole range of mole fractions are typically scarce. Thus, determining a mf and b xv from isobars, as it is often done for pure substances 89 is not a viable option anymore. As an alternative, we proposed fixing the QCE parameters by comparing calculated results to a single liquid phase density at ambient temperature and to the boiling point.…”

Section: B Methodsological Changes To Qcementioning

confidence: 99%

“…Finally, we lifted a restriction on the cluster volumes v ℘ in Peacemaker, which were formerly linearly dependent on the monomer volumes v 1 and v 2 . This restriction was enforced, because it is required to derive the QCE polynomials, 89 but it can be lifted if the exclusion volume is treated as another property that must be determined self-consistently during the QCE iteration. It is now possible to choose any desired cluster volume, as it was done in Weinhold's original work.…”

Section: B Methodsological Changes To Qcementioning

confidence: 99%

“…A simple solution would be to use a smaller initial volume guess, but this may lead to the opposite problem of metastable liquid phases and to convergence problems at high temperatures. In the latest version of our QCE code Peacemaker, 89 we thus perform two complete QCE iterations: one, where we start from the ideal gas volume V id and another, where we start from a low, liquid-like phase volume (e.g., V id /100). We finally choose the results from the iteration that led to the lower Gibbs free energy.…”

Section: B Methodsological Changes To Qcementioning

confidence: 99%

“…89 First, we use the Gibbs energy instead of the free energy to determine convergence, since this is the thermodynamic potential that decides which solution is stable: An iteration has converged, if the relative change in the Gibbs energy is less than a threshold value ε G . Finally, we lifted a restriction on the cluster volumes v ℘ in Peacemaker, which were formerly linearly dependent on the monomer volumes v 1 and v 2 .…”

Section: B Methodsological Changes To Qcementioning

confidence: 99%

“…They can be used to weigh single-cluster properties (e.g., number of hydrogen bonds or quadrupole coupling constants) 38,66 and measure the importance of structural motifs contained in the cluster. 65,66,84,85,89,90 Instead of particle numbers, the percentage of the total number of monomers…”

Section: A Qce Modelmentioning

confidence: 99%

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Quantum cluster equilibrium model of N-methylformamide–water binary mixtures

Domaros

Jähnigen

Friedrich

et al. 2016

The Journal of Chemical Physics

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The established quantum cluster equilibrium (QCE) approach is refined and applied to Nmethylformamide (NMF) and its aqueous solution. The QCE method is split into two iterative cycles: one which converges to the liquid phase solution of the QCE equations and another which yields the gas phase. By comparing Gibbs energies, the thermodynamically stable phase at a given temperature and pressure is then chosen. The new methodology avoids metastable solutions and allows a different treatment of the mean-field interactions within the gas and liquid phases. These changes are of crucial importance for the treatment of binary mixtures. For the first time in a QCE study, the cis-trans-isomerism of a species (NMF) is explicitly considered. Cluster geometries and frequencies are calculated using density functional theory (DFT) and complementary coupled cluster single point energies are used to benchmark the DFT results. Independent of the selected quantum-chemical method, a large set of clusters is required for an accurate thermodynamic description of the binary mixture. The liquid phase of neat NMF is found to be dominated by the cyclic trans-NMF pentamer, which can be interpreted as a linear trimer that is stabilized by explicit solvation of two further NMF molecules. This cluster reflects the known hydrogen bond network preferences of neat NMF. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

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Section: B Methodsological Changes To Qcementioning

confidence: 99%

Section: B Methodsological Changes To Qcementioning

confidence: 99%

Section: B Methodsological Changes To Qcementioning

confidence: 99%

Section: B Methodsological Changes To Qcementioning

confidence: 99%

Section: A Qce Modelmentioning

confidence: 99%

See 3 more Smart Citations

Quantum cluster equilibrium model of N-methylformamide–water binary mixtures

Domaros

Jähnigen

Friedrich

et al. 2016

The Journal of Chemical Physics

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Predicting Vibrational Spectroscopy for Flexible Molecules and Molecules with Non‐Idle Environments

Kirchner

Blasius

Esser

et al. 2020

Advcd Theory and Sims

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Flexible molecules and non‐idle environments can present severe problems in the prediction of vibrational spectra. This work focuses on infrared and vibrational circular dichroism for which the latter is extremely sensitive to such complicated situations. Here two possible ways to perform spectroscopy calculations for such situations are investigated. The first approach is based on static quantum chemical calculations employing cluster‐weighting. The second approach is rooted in ab initio molecular dynamics simulations using the time correlations approach. For the present example ((R)‐butan‐2‐ol), excellent spectra from simulations are obtained for gas and bulk, when the former is averaged over trajectories with all possible starting conformers and these are scaled to match the experimental spectrum. The cluster‐weighted approach is inferior to the simulations but still reaches very good results at much less computational cost. A simplified, but computationally less expensive simulation approach is considered by approximating the electric and magnetic moments, which are input quantities in the correlation function, by classical equations and different populations analysis for the required partial charges. The results are inferior to the full simulations but still give satisfying results at the advantage of being much faster to calculate.

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Dissoziation schwacher Säuren über den gesamten Molenbruchbereich

et al. 2019

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Wir präsentieren am Beispiel von in Wasser gelöster Ameisensäure und Essigsäure, dass der Ansatz der binären Quantum‐Cluster‐Equilibrium‐(bQCE)‐Theorie die Säurestärke über den gesamten Konzentrationsbereich vorhersagen kann. Wir zeigen über einen Molenbruchbereich von 0 bis 0.7, dass die molenbruchabhängige Säurestärke nicht mit simplen Annahmen beschrieben werden kann. Hierin spiegelt sich das komplexe Zusammenspiel verfügbarer dissoziierter Ionen oder konjugierter Basen mit vorhandenen Säure‐ und Wassermolekülen wider. Zusätzlich können unsere berechneten Ionenkonzentrationen das experimentelle Leitfähigkeitsmaximum der Essigsäure mit hervorragender, das der Ameisensäure mit zufriedenstellender Genauigkeit beschreiben. Da für die Ergebnisse nur eine geringe Anzahl an einfachen, quantenchemischen Berechnungen notwendig ist, eignet sich die bQCE‐Theorie als neuer und nützlicher Ansatz, um Eigenschaften nichtwässriger Lösungen vorherzusagen. Die Methode ist außerdem in der Lage, Ionisationsprozesse in hochkonzentrierten Lösungen zu beschreiben, die sowohl für chemische und biologische Systeme wie auch für technologische Prozesse von großer Relevanz sind.

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What can clusters tell us about the bulk?

Cited by 48 publications

References 47 publications

Quantum cluster equilibrium model of N-methylformamide–water binary mixtures

Quantum cluster equilibrium model of N-methylformamide–water binary mixtures

Predicting Vibrational Spectroscopy for Flexible Molecules and Molecules with Non‐Idle Environments

Dissoziation schwacher Säuren über den gesamten Molenbruchbereich

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