Quantum Chemical Study of the Properties of Molecular Hydrogen Complexes of Osmium(II):  A Comparison of Density Functional and Conventionalab InitioMethods

1996 ◽  
Vol 100 (15) ◽  
pp. 6023-6031 ◽  
Author(s):  
Ian Bytheway ◽  
George B. Bacskay ◽  
Noel S. Hush
Keyword(s):  
Quantum Chemical ◽  
Molecular Hydrogen ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study

Quantum chemical study on the formation of isopropyl cyanide and its linear isomer in the interstellar medium

2020 ◽  
pp. 1-11
Author(s):  
Keshav Kumar Singh ◽  
Poonam Tandon ◽  
Alka Misra ◽  
Shivani ◽  
Manisha Yadav ◽  
...  
Keyword(s):  
Amino Acids ◽  
Interstellar Medium ◽  
Gas Phase ◽  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Dark Cloud ◽  
Water Ice ◽  
Hydrocarbon Radicals

Abstract The formation mechanism of linear and isopropyl cyanide (hereafter n-PrCN and i-PrCN, respectively) in the interstellar medium (ISM) has been proposed from the reaction between some previously detected small cyanides/cyanide radicals and hydrocarbons/hydrocarbon radicals. n-PrCN and i-PrCN are nitriles therefore, they can be precursors of amino acids via Strecker synthesis. The chemistry of i-PrCN is especially important since it is the first and only branched molecule in ISM, hence, it could be a precursor of branched amino acids such as leucine, isoleucine, etc. Therefore, both n-PrCN and i-PrCN have significant astrobiological importance. To study the formation of n-PrCN and i-PrCN in ISM, quantum chemical calculations have been performed using density functional theory at the MP2/6-311++G(2d,p)//M062X/6-311+G(2d,p) level. All the proposed reactions have been studied in the gas phase and the interstellar water ice. It is found that reactions of small cyanide with hydrocarbon radicals result in the formation of either large cyanide radicals or ethyl and vinyl cyanide, both of which are very important prebiotic interstellar species. They subsequently react with the radicals CH2 and CH3 to yield n-PrCN and i-PrCN. The proposed reactions are efficient in the hot cores of SgrB2 (N) (where both n-PrCN and i-PrCN were detected) due to either being barrierless or due to the presence of a permeable entrance barrier. However, the formation of n-PrCN and i-PrCN from the ethyl and vinyl cyanide always has an entrance barrier impermeable in the dark cloud; therefore, our proposed pathways are inefficient in the deep regions of molecular clouds. It is also observed that ethyl and vinyl cyanide serve as direct precursors to n-PrCN and i-PrCN and their abundance in ISM is directly related to the abundance of both isomers of propyl cyanide in ISM. In all the cases, reactions in the ice have smaller barriers compared to their gas-phase counterparts.

HYDRATION AND DISSOCIATION OF CALCIUM HYDROXIDE IN WATER CLUSTERS: A QUANTUM CHEMICAL STUDY

2007 ◽  
Vol 06 (03) ◽  
pp. 595-609 ◽  
Author(s):  
CLARA JIAYUN MEN ◽  
FU-MING TAO
Keyword(s):  
Calcium Hydroxide ◽  
Quantum Chemical ◽  
Density Functional ◽  
Water Clusters ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Structure Stability ◽  
Water Molecules ◽  
Aerosol Formation ◽  
Hydrated Clusters

The structure, stability, and properties of the hydrated clusters of calcium hydroxide, Ca ( OH )2( H 2 O )n, n = 1–6, were investigated using density functional and ab initio quantum chemical methods. The results show that six water molecules are needed to result in the complete dissociation of Ca ( OH )2. The stable and ionic conformer of Ca ( OH )2( H 2 O )6 has C 3 symmetry. Its surprising stability and high IR activity render hydrated clusters of Ca ( OH )2 potentially significant in the nucleation of noctilucent clouds in the mesosphere. Trends in the interaction energies (ΔEe) of the complexes show that water molecules in the first shell of Ca 2+ are highly stable, further alluding to the role of hydrated Ca ( OH )2 in aerosol formation.

scholarly journals Quantum chemical study of the structure, spectroscopy and reactivity of NO + .(H 2 O) n =1−5 clusters

2018 ◽  
Vol 376 (2115) ◽  
pp. 20170152 ◽  
Author(s):  
Kirsty A. Linton ◽  
Timothy G. Wright ◽  
Nicholas A. Besley
Keyword(s):  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Ab Initio Molecular Dynamics ◽  
Structure Theory ◽  
Energy Structure ◽  
Hartree Fock ◽  
Quantum Chemical Methods ◽  
Moller Plesset

Quantum chemical methods including Møller–Plesset perturbation (MP2) theory and density functional theory (DFT) have been used to study the structure, spectroscopy and reactivity of NO + .(H 2 O) n =1−5 clusters. MP2/6-311++G** calculations are shown to describe the structure and spectroscopy of the clusters well. DFT calculations with exchange–correlation functionals with a low fraction of Hartree–Fock exchange give a binding energy of NO + .(H 2 O) that is too high and incorrectly predict the lowest energy structure of NO + .(H 2 O) 2 , and this error may be associated with a delocalization of charge onto the water molecule directly binding to NO + . Ab initio molecular dynamics (AIMD) simulations were performed to study the NO + .(H 2 O) 5 H + .(H 2 O) 4 + HONO reaction to investigate the formation of HONO from NO + .(H 2 O) 5 . Whether an intracluster reaction to form HONO is observed depends on the level of electronic structure theory used. Of note is that methods that accurately describe the relative energies of the product and reactant clusters did not show reactions on the timescales studied. This suggests that in the upper atmosphere the reaction may occur owing to the energy present in the NO + .(H 2 O) 5 complex following its formation. This article is part of the theme issue ‘Modern theoretical chemistry’.

scholarly journals Quantum-chemical study of stable, meta-stable and high-pressure alumina polymorphs and aluminum hydroxides

2014 ◽  
Vol 2 (32) ◽  
pp. 13143-13158 ◽  
Author(s):  
Michael F. Peintinger ◽  
Michael J. Kratz ◽  
Thomas Bredow
Keyword(s):  
High Pressure ◽  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Functional Theory ◽  
Aluminum Hydroxides ◽  
Hybrid Density Functional ◽  
Alumina Polymorphs ◽  
Structure Properties

The structure, properties and stability of 7 thermodynamically stable, meta-stable and high-pressure Al2O3 polymorphs and the structure and relative stability of 4 Al hydroxides were calculated with periodic hybrid density functional theory and compared with available experimental data.

scholarly journals QUANTUM-CHEMICAL STUDY OF THE MECHANISM OF REACTION OF DIFORMYLHYDRAZINE WITH p-AMINOPHENOL

2021 ◽  
Vol 1 (1) ◽  
pp. 86-87
Author(s):  
Elena Chirkina
Keyword(s):  
Density Functional Theory ◽  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Functional Theory ◽  
Mechanism Of Reaction ◽  
Theoretical Mechanism

Based on the results of a quantum chemical study within the framework of the elec tron density functional theory by the B3LYP/6-311++G(d, p) method, a theoretical mechanism for the reaction of diformylhydrazine with p-aminophenol is proposed

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