STUDIES OF RATES OF CONVERSION AND POPULATIONS OF VARIOUS CONFORMATIONS OF SATURATED RING COMPOUNDS BY N.M.R.: I. CHLOROCYCLOHEXANE AND BROMOCYCLOHEXANE

1960 ◽  
Vol 38 (8) ◽  
pp. 1241-1248 ◽  
Author(s):  
L. W. Reeves ◽  
K. O. Strømme
Keyword(s):  
Energy Barrier ◽  
Room Temperature ◽  
Carbon Disulphide ◽  
Equilibrium Constants ◽  
Jones Potential ◽  
Lennard Jones ◽  
Ring Compounds ◽  
Saturated Ring ◽  
Van Der Waals Radii ◽  
Bromo Compound

The populations of equatorial and axial halogen forms of chloro- and bromo-cyclohexane have been studied by proton magnetic resonance between 25° and −104 °C in carbon disulphide solution. From the equilibrium constants obtained the free energy change between the two conformations is obtained. The bromo compound has 82% of the equatorial halogen form and the chloro compound 77%. Estimates of the populations are also available for room temperature from the chemical shift measurements. The energy barrier for conversion between the two forms is approximately 10,850 calories. A simple Lennard-Jones potential with the available estimates of van der Waals radii is used to calculate the differences in energy of the two forms.

Modeling and Simulations on CO2 Storage Using Graphene

2014 ◽  
Vol 1079-1080 ◽  
pp. 95-98
Author(s):  
Yung Tsang Chen ◽  
Yue Chan
Keyword(s):  
Carbon Dioxide ◽  
Room Temperature ◽  
Mean Field Theory ◽  
Mean Field ◽  
External Pressure ◽  
Graphene Sheets ◽  
Jones Potential ◽  
Multi Scale ◽  
Lennard Jones ◽  
The Mean

In this paper, we adopt boththe Lennard-Jones potential and the mean field theory to determine themolecular interactions between carbon dioxide and the double layered graphenes.In addition, we employ a modified van der Waals equation which takes into accountthe multi-scale effect in the absorption regime todeduce the gravimetric uptakeof carbon dioxide between graphene sheets. We show that the full absorptionoccurs at rather low external pressure at low temperatures while this happensat roughly 0.2bar at room temperature. The current methodology has the merit ofrapid computational times and producing deductive results in comparison to theusual MD simulations.For graphene sheets of a separation of 10 Å, the maximumgravimetric uptake could reach 13.3 wt.%.

scholarly journals Dislocation Mobility in Two-Dimensional Lennard-Jones Material

1999 ◽  
Vol 578 ◽  
Author(s):  
Nicholas P. Bailey ◽  
James P. Sethna ◽  
Christopher R. Myers
Keyword(s):  
Energy Barrier ◽  
Thermal Activation ◽  
Functional Form ◽  
Finite Energy ◽  
Atomistic Simulations ◽  
Two Dimensional ◽  
Jones Potential ◽  
Lennard Jones ◽  
Accurate Knowledge ◽  
Dimensional Crystal

AbstractIn seeking to understand at a microscopic level the response of dislocations to stress we have undertaken to study as completely as possible the simplest case: a single dislocation in a two dimensional crystal. The intention is that results from this study will be used as input parameters in larger length scale simulations involving many defects. We present atomistic simulations of defect motion in a two-dimensional material consisting of atoms interacting through a modified Lennard-Jones potential. We focus on the regime where the shear stress is smaller than its critical value, where there is a finite energy barrier for the dislocation to hop one lattice spacing. In this regime motion of the dislocation will occur as single hops through thermal activation over the barrier. Accurate knowledge of the barrier height is crucial for obtaining the rates of such processes. We have calculated the energy barrier as a function of two components of the stress tensor in a small system, and have obtained good fits to a functional form with only a few adjustable parameters.

scholarly journals Inferring Single-Cell 3D Chromosomal Structures Based on the Lennard-Jones Potential

2021 ◽  
Vol 22 (11) ◽  
pp. 5914
Author(s):  
Mengsheng Zha ◽  
Nan Wang ◽  
Chaoyang Zhang ◽  
Zheng Wang
Keyword(s):  
Single Cell ◽  
Loss Function ◽  
Gaussian Function ◽  
Three Dimensional ◽  
Lennard Jones Potential ◽  
Jones Potential ◽  
Cubic Lattice ◽  
Lennard Jones ◽  
3D Fish ◽  
Well Depth

Reconstructing three-dimensional (3D) chromosomal structures based on single-cell Hi-C data is a challenging scientific problem due to the extreme sparseness of the single-cell Hi-C data. In this research, we used the Lennard-Jones potential to reconstruct both 500 kb and high-resolution 50 kb chromosomal structures based on single-cell Hi-C data. A chromosome was represented by a string of 500 kb or 50 kb DNA beads and put into a 3D cubic lattice for simulations. A 2D Gaussian function was used to impute the sparse single-cell Hi-C contact matrices. We designed a novel loss function based on the Lennard-Jones potential, in which the ε value, i.e., the well depth, was used to indicate how stable the binding of every pair of beads is. For the bead pairs that have single-cell Hi-C contacts and their neighboring bead pairs, the loss function assigns them stronger binding stability. The Metropolis–Hastings algorithm was used to try different locations for the DNA beads, and simulated annealing was used to optimize the loss function. We proved the correctness and validness of the reconstructed 3D structures by evaluating the models according to multiple criteria and comparing the models with 3D-FISH data.

Raman spectra and lattice dynamics of the α phases of nitrogen and carbon monoxide crystals

1970 ◽  
Vol 48 (19) ◽  
pp. 2265-2271 ◽  
Author(s):  
A. Anderson ◽  
T. S. Sun ◽  
M. C. A. Donkersloot
Keyword(s):  
Carbon Monoxide ◽  
Raman Spectra ◽  
Lattice Dynamics ◽  
Jones Potential ◽  
Lennard Jones ◽  
Neon Laser ◽  
Helium Neon Laser ◽  
First Time ◽  
Helium Neon ◽  
Argon Ion

The Raman spectra of polycrystalline α-nitrogen and α-carbon monoxide have been recorded at 18 °K, using argon–ion and helium–neon laser excitation. Previously undetected peaks at 60 cm−1 for N2 and 90.5 cm−1 for CO are assigned as librational modes, and splitting of the stretching mode in nitrogen is observed for the first time. Spectral features in both the intramolecular and lattice regions are assigned in accordance with accepted crystal structures, and their frequencies compared with those obtained from calculations based on a spherical Lennard–Jones potential and quadrupole–quadrupole interactions between the molecules.

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