scholarly journals Effect of van der Waals interactions on the stability of SiC polytypes

2016 ◽  
Vol 119 (17) ◽  
pp. 175101 ◽  
Author(s):  
Sakiko Kawanishi ◽  
Teruyasu Mizoguchi
Keyword(s):  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
The Stability

scholarly journals General Effect of van der Waals Interactions on the Stability of Alkoxy Intermediates on Metal Surfaces

2017 ◽  
Vol 122 (2) ◽  
pp. 555-560 ◽  
Author(s):  
Yunfei Xu ◽  
Wei Chen ◽  
Efthimios Kaxiras ◽  
Cynthia M. Friend ◽  
Robert J. Madix
Keyword(s):  
Metal Surfaces ◽  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
General Effect ◽  
The Stability

Relative influence of noncovalent interactions on the melting points of a homologous series of 1,2-dibromo-4,5-dialkoxybenzenes

2013 ◽  
Vol 69 (2) ◽  
pp. 204-208 ◽  
Author(s):  
Ana Fonrouge ◽  
Florencia Cecchi ◽  
Pablo Alborés ◽  
Ricardo Baggio ◽  
Fabio D. Cukiernik
Keyword(s):  
Homologous Series ◽  
Noncovalent Interactions ◽  
Present Report ◽  
Van Der Waals ◽  
Halogen Bonding ◽  
Van Der Waals Interactions ◽  
Melting Points ◽  
Acta Cryst ◽  
The Stability ◽  
Aliphatic Chains

Crystal structures are presented for two members of the homologous series of 1,2-dibromo-4,5-dialkoxybenzenes,viz.those with decyloxy and hexadecyloxy substituents, namely 1,2-dibromo-4,5-bis(decyloxy)benzene, C26H44Br2O2, (II), and 1,2-dibromo-4,5-bis(hexadecyloxy)benzene, C38H68Br2O2, (III). The relative influences which halogen bonding, π–π stacking and van der Waals interactions have on these structures are analysed and the results compared with those already found for the lightest homologue, 1,2-dibromo-4,5-dimethoxybenzene, (I) [Cukiernik, Zelcer, Garland & Baggio (2008).Acta Cryst.C64, o604–o608]. The results confirm that the prevalent interactions stabilizing the structures of (II) and (III) are van der Waals contacts between the aliphatic chains. In the case of (II), weak halogen C—Br...(Br—C)′ interactions are also present and contribute to the stability of the structure. In the case of (III), van der Waals interactions between the aliphatic chains are almost exclusive, weaker C—Br...π interactions being the only additional interactions detected. The results are in line with commonly accepted models concerning trends in crystal stability along a homologous series (as measured by their melting points), but the earlier report forn= 1, and the present report forn= 10 and 16, are among the few providing single-crystal information validating the hypothesis.

scholarly journals Thermodynamic basis of the α-helix and DNA duplex

2021 ◽  
Author(s):  
A. I. Dragan ◽  
C. Crane-Robinson ◽  
P. L. Privalov
Keyword(s):  
Hydrogen Bonds ◽  
Double Helix ◽  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
Base Pairs ◽  
The Stability ◽  
Α Helix ◽  
Dna Double Helix ◽  
Conjugate Base ◽  
Thermodynamic Basis

AbstractAnalysis of calorimetric and crystallographic information shows that the α-helix is maintained not only by the hydrogen bonds between its polar peptide groups, as originally supposed, but also by van der Waals interactions between tightly packed apolar groups in the interior of the helix. These apolar contacts are responsible for about 60% of the forces stabilizing the folded conformation of the α-helix and their exposure to water on unfolding results in the observed heat capacity increment, i.e. the temperature dependence of the melting enthalpy. The folding process is also favoured by an entropy increase resulting from the release of water from the peptide groups. A similar situation holds for the DNA double helix: calorimetry shows that the hydrogen bonding between conjugate base pairs provides a purely entropic contribution of about 40% to the Gibbs energy while the enthalpic van der Waals interactions between the tightly packed apolar parts of the base pairs provide the remaining 60%. Despite very different structures, the thermodynamic basis of α-helix and B-form duplex stability are strikingly similar. The general conclusion follows that the stability of protein folds is primarily dependent on internal atomic close contacts rather than the hydrogen bonds they contain.

scholarly journals Unraveling the Stability of Polypeptide Helices: Critical Role of van der Waals Interactions

2011 ◽  
Vol 106 (11) ◽  
Author(s):  
Alexandre Tkatchenko ◽  
Mariana Rossi ◽  
Volker Blum ◽  
Joel Ireta ◽  
Matthias Scheffler
Keyword(s):  
Van Der Waals ◽  
Critical Role ◽  
Van Der Waals Interactions ◽  
The Stability

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

Crystal Structures of Two New Cyclosporin Clathrates

2000 ◽  
Vol 65 (12) ◽  
pp. 1950-1958 ◽  
Author(s):  
Michal Hušák ◽  
Bohumil Kratochvíl ◽  
Ivana Císařová ◽  
Alexandr Jegorov
Keyword(s):  
Crystal Structures ◽  
Methyl Ether ◽  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
Solvent Molecules ◽  
Butyl Methyl Ether

Two isomorphous clathrates formed by dihydrocyclosporin A or cyclosporin V with tert-butyl methyl ether are reported and compared with the structures of related P21-symmetry cyclosporin clathrates. The cyclosporin molecules in both structures are associated via van der Waals interactions forming cavities occupied by solvent molecules (cyclosporin : tert-butyl methyl ether is 1 : 2).

Van der Waals interactions of the disulfide bond revealed: A microwave spectroscopic study of the diethyl disulfide–argon complex

2021 ◽  
Vol 154 (12) ◽  
pp. 124306
Author(s):  
Tao Lu ◽  
Daniel A. Obenchain ◽  
Jiaqi Zhang ◽  
Jens-Uwe Grabow ◽  
Gang Feng
Keyword(s):  
Spectroscopic Study ◽  
Disulfide Bond ◽  
Van Der Waals ◽  
Van Der Waals Interactions
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