scholarly journals Discriminative interactions between chiral molecules: internal discrimination in 1,2-difluorohydrazine

1985 ◽  
Vol 63 (7) ◽  
pp. 1639-1641 ◽  
Author(s):  
Rudolf Zahradník ◽  
Bohdan Schneider ◽  
Pavel Hobza ◽  
Zdenêk Havlas ◽  
Hanspeter Huber
Keyword(s):  
Thermodynamic Properties ◽  
Quantum Chemical ◽  
Short Range ◽  
Energy Surface ◽  
Saddle Points ◽  
Ideal Gas ◽  
Chiral Molecules ◽  
Standard State ◽  
Transition Complex ◽  
Stable Structures

1,2-Difluorohydrazine represents a model for studying short-range discriminative interactions between two chiral radicals. Possible diastereomeric structures of the system were theoretically investigated by means of nonempirical SCF quantum chemical calculations. Four minima and six saddle points separating them were found on the potential energy surface. All the stable structures and one transition complex were completely optimized. Thermodynamic properties for the equilibrium between the two most stable conformers (meso and chiral) of difluorohydrazine are as follows (in kJ/mol): [Formula: see text], [Formula: see text] (standard state: ideal gas at 101.325 kPa, 298 K).

Gas-Phase Clustering of NO+ with H2S and H2O

2007 ◽  
Vol 72 (8) ◽  
pp. 1122-1138 ◽  
Author(s):  
Milan Uhlár ◽  
Ivan Černušák
Keyword(s):  
Hydrogen Bonds ◽  
Water Molecule ◽  
Gas Phase ◽  
Saddle Points ◽  
Solvent Molecule ◽  
Local Minima ◽  
Additional Water ◽  
Three Body ◽  
Rain Formation ◽  
Stable Structures

The complex NO+·H2S, which is assumed to be an intermediate in acid rain formation, exhibits thermodynamic stability of ∆Hº300 = -76 kJ mol-1, or ∆Gº300 = -47 kJ mol-1. Its further transformation via H-transfer is associated with rather high barriers. One of the conceivable routes to lower the energy of the transition state is the action of additional solvent molecule(s) that can mediate proton transfer. We have studied several NO+·H2S structures with one or two additional water molecule(s) and have found stable structures (local minima), intermediates and saddle points for the three-body NO+·H2S·H2O and four-body NO+·H2S·(H2O)2 clusters. The hydrogen bonds network in the four-body cluster plays a crucial role in its conversion to thionitrous acid.

Molecular Dynamic Simulation of Carbon Nanostructures Formation

2014 ◽  
Vol 1040 ◽  
pp. 92-96
Author(s):  
Denis A. Tatarnikov ◽  
Aleksey V. Godovykh
Keyword(s):  
Thermodynamic Properties ◽  
Molecular Dynamic Simulation ◽  
Molecular Dynamic ◽  
Dynamic Simulation ◽  
Carbon Nanostructures ◽  
Carbon Nanomaterials ◽  
Statistical Data ◽  
New Materials ◽  
Molecular Dynamic Simulation Study ◽  
Stable Structures

This paper is devoted to the study of stable structures of various carbon nanomaterials using molecular dynamic simulation, study of their properties and characteristics, as well as search for possible later use in nanoelectronics and nanomechanics. We develop programs for computation of the system of atoms at every step and visualization of that data, also we research of thermodynamic properties and conditions of formation of different carbon nanostructures, try to predict existence of new materials. Nowadays we have two separate programs: one for computation and one for visualization. We continue to collect statistical data, investigate behavior of the system under different conditions.

scholarly journals The role of ammonia in sulfuric acid ion induced nucleation

2008 ◽  
Vol 8 (11) ◽  
pp. 2859-2867 ◽  
Author(s):  
I. K. Ortega ◽  
T. Kurtén ◽  
H. Vehkamäki ◽  
M. Kulmala
Keyword(s):  
Sulfuric Acid ◽  
Quantum Chemical ◽  
Local Minimum ◽  
Good Accuracy ◽  
Energy Surface ◽  
Ground Level ◽  
Computational Effort ◽  
Free Energy Surface ◽  
Large Clusters

Abstract. We have developed a new multi-step strategy for quantum chemical calculations on atmospherically relevant cluster structures that makes calculation for large clusters affordable with a good accuracy-to-computational effort ratio. We have applied this strategy to evaluate the relevance of ternary ion induced nucleation; we have also performed calculations for neutral ternary nucleation for comparison. The results for neutral ternary nucleation agree with previous results, and confirm the important role of ammonia in enhancing the growth of sulfuric acid clusters. On the other hand, we have found that ammonia does not enhance the growth of ionic sulfuric acid clusters. The results also confirm that ion-induced nucleation is a barrierless process at high altitudes, but at ground level there exists a barrier due to the presence of a local minimum on the free energy surface.

Ideal gas thermodynamic properties of phenol and cresols

1978 ◽  
Vol 7 (2) ◽  
pp. 417-423 ◽  
Author(s):  
S. A. Kudchadker ◽  
A. P. Kudchadker ◽  
R. C. Wilhoit ◽  
B. J. Zwolinski
Keyword(s):  
Thermodynamic Properties ◽  
Ideal Gas
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