scholarly journals Structural Conformational Study of Eugenol Derivatives Using Semiempirical Methods

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Radia Mahboub
Keyword(s):  
Strain Energy ◽  
Semiempirical Methods ◽  
Am1 Method ◽  
Molecular Orbital Calculations ◽  
Torsional Angle ◽  
Conformational Structure ◽  
Pm3 Method ◽  
Eugenyl Acetate ◽  
Angle Effect ◽  
The Stability

We investigated the conformational structure of eugenol and eugenyl acetate under torsional angle effect by performing semiempirical calculations using AM1 and PM3 methods. From these calculations, we have evaluated the strain energy of conformational interconversion. To provide a better estimate of stable conformations, we have plotted the strain energy versus dihedral angle. So, we have determined five geometries of eugenol (three energy minima and two transition states) and three geometries of eugenyl acetate (two energy minima and one transition state). From the molecular orbital calculations, we deduce that the optimized trans form by AM1 method is more reactive than under PM3 method. We can conclude that both methods are efficient. The AM1 method allows us to determine the reactivity and PM3 method to verify the stability.

Tautomerism in Five-membered Nitrogen Heterocycles. A Test of the Reliability of Semiempirical (AMI, PM3, MNDO) Quantum Chemical Methods

1990 ◽  
Vol 45 (11-12) ◽  
pp. 1328-1334 ◽  
Author(s):  
Walter M. F. Fabian
Keyword(s):  
Quantum Chemical ◽  
Dipole Moments ◽  
Nitrogen Heterocycles ◽  
Ionization Potentials ◽  
Semiempirical Methods ◽  
Chemical Methods ◽  
Pm3 Method ◽  
Lone Pairs ◽  
Quantum Chemical Methods ◽  
The Stability

AbstractThe reliability of three popular semiempirical quantum chemical methods (AM1, PM3, MNDO) for the treatment of tautomeric equilibria is tested in a series of five-membered nitrogen heterocycles. The known flaw of MNDO to overestimate the stability of compounds with two or more adjacent pyridine-like lone pairs is also present in AM1 and to a somewhat lesser extent in PM3. Tautomeric species differing in the number of adjacent pyridine-like lone pairs, thus, cannot be adequately treated by these semiempirical methods. Both AM1 as well as PM3, however, represent major improvements over MNDO in the case of lactam-lactim tautomerism. The stability of N-oxides as compared to N-hydroxy tautomers seems to be overestimated by the PM3 method. All three semiempirical methods yield quite reliable ionization potentials and dipole moments.

Study of Hydrogen Bonding in Carboxylic Acids by the MNDO/M Method

1994 ◽  
Vol 59 (6) ◽  
pp. 1251-1260 ◽  
Author(s):  
Michal Bureš ◽  
Jaroslav Bezus
Keyword(s):  
Experimental Data ◽  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Carboxylic Acids ◽  
Promising Method ◽  
Semiempirical Methods ◽  
Am1 Method ◽  
Bond Lengths ◽  
Pm3 Method

The semiempirical methods MNDO/M, AM1 and PM3 were applied to the study of hydrogen bonds in carboxylic acids. The calculated hydrogen bond lengths and enthalpies of dimerization were compared with experimental data. The AM1 method fails to properly describe systems with strong hydrogen bonds. The PM3 method predicts the hydrogen bond lengths correctly but underestimates systematically the enthalpies of dimerization. MNDO/M appears to be a promising method for the treatment of association of carboxylic acids.

Evaluation of the Stability of Raft Structure in Nickel Base Superalloys Throughout their Lifetime

2006 ◽  
Vol 980 ◽  
Author(s):  
Katsushi Tanaka ◽  
Toru Inoue ◽  
Tetsu Ichitsubo ◽  
Kyosuke Kishida ◽  
Haruyuki Inui
Keyword(s):  
Strain Energy ◽  
Lattice Misfit ◽  
Gamma Prime ◽  
Lamellar Interface ◽  
Nickel Base Superalloys ◽  
Nickel Base ◽  
The Stability ◽  
Numerical Calculation Method ◽  
Creep Deformations ◽  
Lamellar Interfaces

AbstractStability of raft structure in nickel base superalloys has been examined by using elastic energy calculations based on a microelasticity theory. The numerical calculation method for a structurally heterogeneous system is applied. The results indicate that the raft structure is significantly stabilized by introductions of creep deformations till the critical creep deformation at which the lattice misfit between gamma and gamma-prime phases is completely compensated by creep dislocations. When the magnitude of creep deformations exceed the critical value, the (001) lamellar interfaces become elastically unstable and a tilted lamellar interface become the most stable one. This instability of the 001 raft structure leads a tilted or wavy lamellar interfaces for reducing the internal strain energy, that is a precursor to collapse the raft structure.

MNDO calculations for some allotropes, hydrides, and oxides of phosphorus

1984 ◽  
Vol 62 (2) ◽  
pp. 341-347 ◽  
Author(s):  
N. Colin Baird
Keyword(s):  
Molecular Orbital ◽  
Strain Energy ◽  
Mndo Method ◽  
Molecular Orbital Calculations ◽  
Mndo Calculations

Molecular orbital calculations by the MNDO method are reported for some allotropes, hydrides, and oxides of phosphorus. The aim of the study is to test further the ability of MNDO to reproduce the energetics of PP, PH, and PO bonds, and to apply MNDO to interesting problems in the chemistry of such systems. Different isomers of P4, P6, and P8 are considered, as well as ions of P3, P5, and P7. The method is found to overestimate strain energy in three-membered rings, and to underestimate the strength of three-electron PP bonds. The strength of PO π bonds apparently also is overestimated. Possible isomers of P2O2 and P2O3 are discussed.

Instabilities and Point Defects at Step-Free Si(001) and (111) Terraces During High Temperature Annealing

1999 ◽  
Vol 587 ◽  
Author(s):  
Doohan Lee ◽  
Jack M. Blakely
Keyword(s):  
High Temperature ◽  
Point Defect ◽  
Point Defects ◽  
Strain Energy ◽  
Annealing Temperature ◽  
Small Islands ◽  
High Temperature Annealing ◽  
Atomic Steps ◽  
The Stability

AbstractIn this paper we describe observations on the stability of extremely large Si(001) and (111) terraces that are formed by a technique described previously. Following annealing at high temperature and quenching, a series of concentric pits of monoatomic depth are observed with spacing between successive pits of the order of several microns; pits do not form on (111) until the terraces get extremely large. The occurrence of small islands or small pits on the terraces of quenched samples gives information on the majority point defect at the annealing temperature. On (001) samples that are slowly cooled from the annealing temperature, it is observed that pairs of atomic steps have formed on the large terrace; we believe that these result from the tendency of the surface to minimize the strain energy associated with the (2 × 1) reconstruction.

Comparison of Theoretical Approaches Predicting the Coherent-Semicoherent Transition in Nanoscale Axial Heterostructures

2014 ◽  
Vol 1664 ◽  
Author(s):  
Thomas Riedl ◽  
Joerg K.N. Lindner
Keyword(s):  
Strain Energy ◽  
Critical Thickness ◽  
Optoelectronic Devices ◽  
The Other ◽  
Misfit Dislocations ◽  
Strain Partitioning ◽  
Theoretical Approaches ◽  
Elastic Mismatch ◽  
The Stability

ABSTRACTThe formation of misfit dislocations is an important issue for the performance of heteroepitaxial micro- and optoelectronic devices. We analyze three approaches that quantify the stability of misfit dislocations in axial-heteroepitaxial nanowires with respect to applicability and predictions of critical nanowire dimensions. The “nanoheteroepitaxy” approach of Zubia and Hersee proves suitable for determination of strain partitioning in the presence of an elastic mismatch. Concerning the critical thickness and diameter however the descriptions of Ertekin et al. and Glas respectively yield more reliable results, owing to the consideration of the total coherent and dislocation related energies plus the residual strain energy. In contrast to the model of Ertekin et al., which refers to infinitely long nanowires, the other two mentioned approaches allow predictions of the critical thickness of mismatched deposits on the nanowire axial face.

scholarly journals Improving the energy method for calculating beams with a narrow rectangular section on the side buckling

2020 ◽  
Vol 164 ◽  
pp. 02033
Author(s):  
Serdar Yazyev ◽  
Anastasia Lapina ◽  
Ivan Zotov ◽  
Anton Chepurnenko ◽  
Irina Doronkina
Keyword(s):  
Analytical Solution ◽  
Total Energy ◽  
Energy Method ◽  
Strain Energy ◽  
Vertical Displacement ◽  
Center Of Gravity ◽  
Rectangular Section ◽  
Minimum Total Energy ◽  
The Stability ◽  
External Forces

We propose an improved version of the energy method in calculating rectangular beams for the stability of a flat bending shape. The essence of this variant of the method is to use the principle of the minimum total energy instead of the condition for the equality of the potential strain energy and the work of external forces. This version of the method makes it easy to obtain a numerical-analytical solution for any number of members of series. The solution of the problem for a pivotally supported beam is presented taking into account the vertical displacement of the load relative to the center of gravity.

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