Peptide models XV. The effect of basis set size increase and electron correlation on selected minima of the ab initio 2D-Ramachandran map of For-Gly-NH2 and For-l-Ala-NH2

1997 ◽  
Vol 391 (1-2) ◽  
pp. 15-26 ◽  
Author(s):  
G. Endrédi ◽  
A. Perczel ◽  
O. Farkas ◽  
M.A. McAllister ◽  
G.I. Csonka ◽  
...  
Keyword(s):  
Ab Initio ◽  
Electron Correlation ◽  
Basis Set ◽  
Size Increase ◽  
Set Size ◽  
Ramachandran Map ◽  
Peptide Models

Conformational Structure of Chloromethyldichlorophosphines

2002 ◽  
Vol 57 (6-7) ◽  
pp. 333-336
Author(s):  
Evgenii A. Romanenko ◽  
Alexander M. Nesterenko
Keyword(s):  
Experimental Data ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electron Correlation ◽  
Basis Set ◽  
Conformational Structure ◽  
Gauche Conformation ◽  
Nuclear Quadrupole ◽  
Set Up ◽  
Good Agreement

IThe 35Cl nuclear quadrupole resonances (77 K) and ab initio calculations of trichloromethyldichlorophosphine () show that it exists in the chess conformation form. The barrier to internal rotation about the P-C bond in I at the RHF/6-31++ G(d,p) level equals to 38.1 kJ mol-1. In chloromethyldichlorophosphine (II) the extension of the basis set up to the RHF/6-311++G(df, pd) level does not improve the description of the most preferable gauche-conformation; only if electron correlation (at the MP2 level) is taken into account the results are in a good agreement with experimental data.

Ab initio molecular orbital study of the effects of basis set size on the calculated structure and acidity of hydroxyl groups in framework molecular sieves

1992 ◽  
Vol 96 (25) ◽  
pp. 10247-10257 ◽  
Author(s):  
John B. Nicholas ◽  
Randall E. Winans ◽  
Robert J. Harrison ◽  
Lennox E. Iton ◽  
Larry A. Curtiss ◽  
...  
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Molecular Sieves ◽  
Basis Set ◽  
Hydroxyl Groups ◽  
Set Size ◽  
Molecular Orbital Study ◽  
Orbital Study

Ab initio study of the structure of the hydrogen maleate anion

1993 ◽  
Vol 71 (3) ◽  
pp. 303-306 ◽  
Author(s):  
Miguel A. Ríos ◽  
Jesús Rodríguez
Keyword(s):  
Hydrogen Bond ◽  
Proton Transfer ◽  
Ab Initio ◽  
Electron Correlation ◽  
Basis Set ◽  
Ab Initio Methods ◽  
Ab Initio Study ◽  
Barrier Heights ◽  
Minimum Potential ◽  
Complete Optimization

The hydrogen maleate ion was studied by ab initio methods with complete optimization at the 3-21G, 6-31G, 6-31G**, and 6-31+G(2d,1p) levels. To study the influence of electron correlation, MP2 calculations have been done for the 6-31G** geometry. All calculations at the HF level predicted an asymmetric hydrogen bond with a double minimum potential governing transfer between the two equivalent structures. Moreover, both asymmetry and proton transfer barrier increase systematically with the power of the basis set used, with calculated barrier heights of 0.12 (3-21G), 1.59 (6-31G), 1.64 (6-31G**), and 2.00 kcal/mol (6-31+G). Only the introduction of the electron correlation at the MP2 level seems to predict a single minimum potential.

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