Ab initio Studies on Hydrazines: 4H-1,2,4-Triazol-4-amine

1989 ◽  
Vol 42 (10) ◽  
pp. 1623 ◽  
Author(s):  
NV Riggs
Keyword(s):  
Saddle Point ◽  
Relative Intensity ◽  
Vibrational Energy ◽  
Zero Point ◽  
Equilibrium Structure ◽  
Vibrational Frequencies ◽  
Basis Sets ◽  
Transition Structure ◽  
Intensity Pattern ◽  
Zero Point Vibrational Energy

The geometries of four stationary structures of 4H-1,2,4-triazol-4-amine have been optimized with the 3-21g and 3-21g(N*) basis sets. The lowest-energy and only equilibrium structure predicted by these calculations is the 'perpendicular' CS form (7). All its calculated vibrational frequencies are real and, after zero-point vibrational-energy corrections, it lies 26.9 kJ mol-1 below the 'parallel' C, structure (6), here characterized as the transition structure for internal rotation about the N-NH2 bond (cf. 26.5 kJ mol-1 for the corresponding structures of 1H-pyrrol-1-amine, but only 8.7 kJ mol-1 for the corresponding structures of 2H-1,2,3-triazol-2-amine). The transition structure for inversion at the NH2 centre is, as for 1H-pyrrol-1-amine and 2H-1,2,3-triazol-2-amine, the perpendicular C2v � structure (5), the barrier being 21.4 kJ mol-1 (cf. 24-26 kJ mol-1 for the two reference azolamines ). The planar C2v structure (4) is a second-order saddle point lying 66.6 kJ mol-1 above the equilibrium structure (cf. 69.4 kJ mol-1 for 1H-pyrrol-1-amine, but only 41 .7 kJ mol-1 for 2H-1,2,3-triazol-2-amine). The calculated NH-stretching vibrational frequencies for 4H-1,2,4-triazol-4-amine are c. 20 cm-1 higher than those of 1H-pyrrol-1-amine and their splitting is c. 8 cm-1 greater but they show a very similar relative-intensity pattern, quite unlike that calculated for 2H-1,2,3-triazol-2-amine. ′

Ab initio Studies on Hydrazines: 1H-Pyrrol-1-amine (N-Aminopyrrole)

1988 ◽  
Vol 41 (3) ◽  
pp. 397 ◽  
Author(s):  
NV Riggs ◽  
L Radom
Keyword(s):  
Saddle Point ◽  
Ab Initio ◽  
Pyrrole Ring ◽  
Vibrational Energy ◽  
Zero Point ◽  
Equilibrium Structure ◽  
Basis Sets ◽  
Primary Amines ◽  
Transition Structure ◽  
Zero Point Vibrational Energy

The geometries of four stationary structures of 1H-pyrrol-1-amine have been optimized with the 3-21G and 3-21G(N*) basis sets. The lowest- energy and only equilibrium structure is the 'perpendicular' CS form (4) in which a pyramidal NH2 group is bisected by the plane of the pyrrole ring. The transition structure for inversion at the NH2 group is the perpendicular C2V form (2). After zero-point vibrational -energy corrections, it lies 24.5 kJ mol-1 [3-21G(N*)] above (4). The transition structure for rotation about the N-NH2 bond is the 'parallel' CS form (3) in which a plane of symmetry bisects both the pyrrole ring and the attached pyramidal NH2 group; it lies 26.5 kJ mol-1 above (4). The planar C2V structure (1) is a second-order saddle point lying 69.4 kJ mol-1 above (4). The spacing of NH-stretching frequencies calculated for the equilibrium structure (4) of 1H-pyrrol-1-amine is in the range for normal primary amines, unlike that for 1,1-dimethylhydrazine.

Ab initio Studies on Hydrazines: 2H-1,2,3-Triazol-2-amine With Special Reference to Its Equilibrium Structure and Vibrational Spectrum

1989 ◽  
Vol 42 (3) ◽  
pp. 433 ◽  
Author(s):  
NV Riggs
Keyword(s):  
Hydrogen Bonding ◽  
Vibrational Energy ◽  
Zero Point ◽  
Equilibrium Structure ◽  
Basis Sets ◽  
Transition Structure ◽  
Hydrogen Atoms ◽  
Ring Nitrogen ◽  
Experimental Values ◽  
Double Hydrogen

The geometries of four stationary structures of 2H-1,2,3-triazol-2-amine have been optimized with the 3-21G and 3-21G(N*) basis sets. The lowest-energy and only equilibrium structure predicted by these calculations is the 'perpendicular' Cs form (3), whereas infrared studies on benzo-annelated analogues had suggested it might be the 'parallel' Cs form (2) stabilized by 'double hydrogen-bonding' of the amino-hydrogen atoms to the flanking ring-nitrogen atoms. The latter form (2) is here characterized as the transition structure for rotation about the N-NH2 bond and, after zero-point vibrational-energy corrections, is calculated to lie 8.7 kJ mol-1 above the equilibrium structure (3) at HF/3-21G(N*) level or only 3.8 kJ mol-1 at MP4/6-31G** level. This very low barrier to internal rotation (cf. 26.5 kJ mol-1 for the analogous 1H-pyrrol-1-amine) may be due to double hydrogen-bonding of the kind suggested by the experimental study mentioned above. The transition structure for inversion at the NH2 centre is, as for 1H-pyrrol-1-amine, the perpendicular C2v structure (5), the barrier being 25.8 kJ mol-1 (cf. 24.5 kJ mol-1 for 1H-pyrrol-1-amine), and the planar C2v structure (4) is a second-order saddle point lying 41.7 kJ mol-1 above the equilibrium structure (3). Calculated NH-stretching frequencies, their separation, and relative intensities as compared with experimental values for benzo-annelated analogues offer broad support for the assignments above based on relative energies.

An ab initio Study of the Equilibrium Structures of Prop-2-ynamine (Propargylamine) and the Transition Structures Connecting Them

1987 ◽  
Vol 40 (3) ◽  
pp. 435 ◽  
Author(s):  
NV Riggs
Keyword(s):  
Ab Initio ◽  
Internal Rotation ◽  
Vibrational Energy ◽  
Vibrational Analysis ◽  
Zero Point ◽  
Basis Set ◽  
Basis Sets ◽  
Experimental Result ◽  
Transition Structure ◽  
Equilibrium Structures

Optimization with the 3-21G and 3-21G(N*) basis sets finds, in agreement with previous ab initio studies and the experimental result, the anti conformation of prop-2-ynamine to be of lowest energy and, after zero-point vibrational -energy ( Ezpv ) corrections, the gauche form to lie 11 kJ mol-l higher; by vibrational analysis, both are confirmed as equilibrium structures. The synform was not able to be optimized with the 3.21G basis set but, with the 3-21G(N*) basis set, is found to lie 8.6 kJ mol-1 (after Ezpv corrections) above the gauche form, and is shown by vibrational analysis to be a transition structure connecting enantiomeric gauche forms by internal rotation about the N-C bond. The transition structure connecting gauche and anti forms by internal rotation lies 6.3 kJ mol-1 (after Ezpv corrections) above the gauche form, and the transition structure for inversion at the nitrogen atom lies 31.1 kJ mol- l (after Ezpvcorrections) above the anti form.

ON THE NECKING-IN PROCESS IN CLUSTER DECAYS

1990 ◽  
Vol 05 (20) ◽  
pp. 3901-3928 ◽  
Author(s):  
K. DEPTA ◽  
J. A. MARUHN ◽  
HOU-JI WANG ◽  
A. SĂNDULESCU ◽  
W. GREINER ◽  
...  
Keyword(s):  
Potential Energy Surfaces ◽  
Vibrational Energy ◽  
Correction Term ◽  
Zero Point ◽  
Alpha Decay ◽  
Shell Correction ◽  
Macroscopic Models ◽  
Excellent Description ◽  
Energy Surfaces ◽  
Zero Point Vibrational Energy

Two new macroscopic models (liquid drop and Yukawa-plus-exponential) describing the decays with emission of large fragments including alpha decay are developed. The proposed shape parametrization consists of two intersecting spheres smoothly joined by a third "rolling sphere". The first two spheres describe asymptotically the charge and mass asymmetries and the third one the necking-in process. It is shown that the potential energy surfaces in the neck and the relative distance between the centers of the spheres (for a given mass and charge fragmentation) lead to different dynamical paths depending on the mass and charge of the emitted fragment. Along the path a phenomenological shell correction term and a zero point vibrational energy are introduced. It is shown that this model gives an excellent description of the present experimental data.

Zero-point vibrational energy of an adsorbed film

1991 ◽  
Vol 84 (1-2) ◽  
pp. 1-17 ◽  
Author(s):  
James F. Annett ◽  
Milton W. Cole ◽  
Peter B. Shaw ◽  
Richard M. Stratt
Keyword(s):  
Vibrational Energy ◽  
Zero Point ◽  
Adsorbed Film ◽  
Zero Point Vibrational Energy

AB INITIO STUDY OF SPECTROSCOPIC CONSTANTS AND ANHARMONIC FORCE FIELD OF AsH2 RADICAL

2011 ◽  
Vol 10 (06) ◽  
pp. 849-860 ◽  
Author(s):  
YURONG GUO ◽  
MEISHAN WANG ◽  
CHUANLU YANG ◽  
YUTING SUN ◽  
ZILIANG ZHU
Keyword(s):  
Force Field ◽  
Experimental Studies ◽  
Dft Method ◽  
Equilibrium Structure ◽  
Vibrational Frequencies ◽  
Force Constants ◽  
Basis Sets ◽  
Spectroscopic Constants ◽  
Rotational Constants ◽  
Anharmonic Force

The equilibrium structure, spectroscopic constants and anharmonic force field of AsH2 have been investigated at B3LYP, B3PW91 and MP2 methods employing the basis sets of cc-pVNZ and aug-cc-pVNZ (N ∈ { T , Q }), respectively. The computed geometries, rotational constants, part of vibrational frequencies, quartic and sextic centrifugal distortion constants are compared with the available experimental data or theoretical results. The other vibrational frequencies, equilibrium rotational constants, anharmonic constants, vibration–rotation interaction constants, cubic and quartic force constants of AsH2 are also predicted for the first time. Furthermore, the calculated results show that the DFT method is superior to MP2 at the calculations of geometries, spectroscopic constants and force constants. The B3PW91/aug-cc-pVQZ results are more reliable. Our predictions can provide useful data for the experimental studies of the corresponding spectroscopic constants of AsH2 .

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