A computational study on the structures of methylamine–carbon dioxide–water clusters: evidence for the barrier free formation of the methylcarbamic acid zwitterion (CH3NH2+COO−) in interstellar water ices

2011 ◽  
Vol 13 (23) ◽  
pp. 11083 ◽  
Author(s):  
Hakan Kayi ◽  
Ralf I. Kaiser ◽  
John D. Head
Keyword(s):  
Carbon Dioxide ◽  
Water Clusters ◽  
Computational Study ◽  
Barrier Free

Proton Acidity and Proton Mobility in ECR-40, a Silicoaluminophosphate That Violates Löwenstein’s Rule

2019 ◽  
Author(s):  
Michael Fischer
Keyword(s):  
Density Functional ◽  
Water Clusters ◽  
Computational Study ◽  
Acid Catalyst ◽  
Ab Initio Molecular Dynamics ◽  
Brønsted Acidity ◽  
Hydrothermal Route ◽  
Proton Mobility ◽  
Brönsted Acidity ◽  
A Minor

<p>The silicoaluminophosphate zeotype ECR-40, which has the MEI topology, contains linkages of AlO<sub>4</sub> tetrahedra via a common oxygen atom, thereby violating the famous “Löwenstein’s rule”. Due to the proven existence of Al-O-Al linkages in this material, it constitutes an ideal model system to study the acidity and mobility of protons associated with such unusual linkages. In addition, their properties can be directly compared to those of protons associated with more common Si-O-Al linkages, which are also present in ECR-40. In this work, static density functional theory (DFT) calculations including a dispersion correction were employed to study the preferred proton sites as well as the Brønsted acidity of the framework protons, followed by DFT-based ab-initio molecular dynamics (AIMD) to investigate the proton mobility in guest-free and hydrated ECR-40. Initially, two different proton arrangements were compared, one containing both H[O6] protons associated with Al-O-Al linkages and H[O10] protons at Si-O-Al linkages, the other one containing only H[O10] protons. The former model was found to be thermodynamically favoured, as a removal of protons from the Al-O-Al linkages causes a local accumulation of negative charge. Calculations of the deprotonation energy showed a moderately higher Brønsted acidity of the H[O10] protons, at variance with previous empirical explanations, which attributed the exceptional performance of ECR-40 as acid catalyst to the presence of Al‑O‑Al linkages. The AIMD simulations (<i>T</i> = 298 K) delivered no appreciable proton mobility for guest-free ECR-40 and for low levels of hydration (one H<sub>2</sub>O per framework proton). Under saturation conditions, framework deprotonation occurred, leading to the formation of protonated water clusters in the pores. Pronounced differences between the two types of framework protons were observed: While the H[O10] protons were always removed from the Si-O-Al linkages, the Al-O-Al linkages remained mostly protonated, but deprotonation did occur to a minor extent. The observation of a degree of framework deprotonation of Al-O-Al linkages differs from the findings reported in a recent computational study of hydrated aluminosilicate zeolites with such linkages (Heard et al., <i>Chem. Sci.</i> <b>2019</b>, <i>10</i>, 5705), pointing to an influence of the overall framework composition. Further inspection of the AIMD results showed that a coordination of water molecules to framework Al atoms occurred in many cases, especially in the vicinity of the Al-O-Al linkages, sometimes resulting in a pronounced modification of the linkages through additional bridging oxygen atoms. Given the changes in the local structure, it can be expected that such modified linkages are especially prone to break upon dehydration. Thus, in addition to elucidating the deprotonation behaviour of protons associated with different types of linkages, the calculations also provide insights into possible reasons for the instability of Al-O-Al linkages, clarifying why Löwenstein’s rule is mostly obeyed in materials that are formed via a hydrothermal route.</p>

scholarly journals How bulk and surface properties of Ti4SiC3, V4SiC3, Nb4SiC3 and Zr4SiC3 tune reactivity: A computational study

2021 ◽  
Author(s):  
Matthew Quesne ◽  
C. Richard A. Catlow ◽  
Nora Henriette De Leeuw
Keyword(s):  
Carbon Dioxide ◽  
Transition Metal ◽  
Surface Properties ◽  
In Silico ◽  
Computational Study ◽  
Max Phase ◽  
Early Transition Metal ◽  
Silicon Carbides ◽  
Carbon Dioxide Hydrogenation ◽  
Early Transition

We present several in silico insights into the MAX-phase of early transition metal silicon carbides and explore how these affect carbon dioxide hydrogenation. Periodic desity functional methodology is applied to...

Conformational structures of jet-cooled acetaminophen–water clusters: a gas phase spectroscopic and computational study

2017 ◽  
Vol 19 (6) ◽  
pp. 4840-4848 ◽  
Author(s):  
Ahreum Min ◽  
Ahreum Ahn ◽  
Cheol Joo Moon ◽  
Ji Hoon Lee ◽  
Yeon Guk Seong ◽  
...  
Keyword(s):  
Gas Phase ◽  
Water Clusters ◽  
Computational Study ◽  
Theoretical Calculations

Jet-cooled acetaminophen (AAP)–water clusters, AAP–(H2O)1, have been investigated by a combination of theoretical calculations and R2PI, UV–UV HB, IR-dip, IR–UV HB techniques in the gas phase.

Analysis of Avoided Carbon-Dioxide Due to Photovoltaic and Wind Turbine Technologies Displacing Electrical Peaking Facilities

2009 ◽  
Author(s):  
Jarod C. Kelly ◽  
Deepak Sivaraman ◽  
Gregory A. Keoleian
Keyword(s):  
Carbon Dioxide ◽  
Renewable Energy ◽  
Carbon Dioxide Emissions ◽  
Computational Study ◽  
San Antonio ◽  
Carbon Dioxide Emission ◽  
Renewable Energy Technologies ◽  
Energy Technologies ◽  
The Impact ◽  
Renewable Technology

Many studies that examine the impact of renewable energy installations on avoided carbon-dioxide utilize national, regional or state averages to determine the predicted carbon-dioxide offset. The approach of this computational study was to implement a dispatching strategy in order to determine precisely which electrical facilities would be avoided due to the installation of renewable energy technologies. This study focused on a single geographic location for renewable technology installation, San Antonio, Texas. The results indicate an important difference between calculating avoided carbon-dioxide when using simple average rates of carbon-dioxide emissions and a dispatching strategy that accounts for the specific electrical plants used to meet electrical demands. The avoided carbon-dioxide due to renewable energy technologies is overestimated when using national, regional and state averages. This occurs because these averages include the carbon-dioxide emission factors of electrical generating assets that are not likely to be displaced by the renewable technology installation. The study also provides a comparison of two specific renewable energy technologies: photovoltaics (PV) and wind turbines. The results suggest that investment in PV is more cost effective for the San Antonio location. While the results are only applicable to this location, the methodology is useful for evaluating renewable technologies at any location.

Computational study of the dissociation of H–X acids (X=F, Cl, Br, I) in water clusters

2002 ◽  
Vol 117 (7) ◽  
pp. 3160-3168 ◽  
Author(s):  
Enrique M. Cabaleiro-Lago ◽  
Jose M. Hermida-Ramón ◽  
Jesús Rodrı́guez-Otero
Keyword(s):  
Water Clusters ◽  
Computational Study

Base initiated depolymerization of polycarbonates to epoxide and carbon dioxide co-monomers: a computational study

2013 ◽  
Vol 15 (6) ◽  
pp. 1578 ◽  
Author(s):  
Donald J. Darensbourg ◽  
Andrew D. Yeung ◽  
Sheng-Hsuan Wei
Keyword(s):  
Carbon Dioxide ◽  
Computational Study

Carbon dioxide–water clusters in the atmosphere of Mars

2011 ◽  
Vol 965 (2-3) ◽  
pp. 353-358 ◽  
Author(s):  
I.K. Ortega ◽  
A. Määttänen ◽  
T. Kurtén ◽  
H. Vehkamäki
Keyword(s):  
Carbon Dioxide ◽  
Water Clusters

Carbon Dioxide Insertion into Diamines: A Computational Study of Solvent Effects

ChemSusChem ◽  
2012 ◽  
Vol 5 (10) ◽  
pp. 1967-1973 ◽  
Author(s):  
Wilhelm A. Eger ◽  
Alexander Genest ◽  
Bernhard Rieger ◽  
Notker Rösch
Keyword(s):  
Carbon Dioxide ◽  
Solvent Effects ◽  
Computational Study
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