Study of the structural and thermodynamic stability of pentacoordinated nitrogen compounds NF2X3 (X = H, Cl, Br): Ab initio calculations

Getmanskii, Iliya V.; Minyaev, R. M.

doi:10.1007/s10947-008-0168-3

Cited by 9 publications

(12 citation statements)

References 19 publications

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“…For complex systems, the potential energy surface becomes more complicated, and transitions from a potential basin to another involve not only index-one saddles but also higher index saddles [55][56][57][58][59][60][61][62][63]. Recently the role of index-two saddle was revealed several dynamical aspects.…”

Section: Pechukas and Pollakmentioning

confidence: 99%

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Reactivity boundaries to separate the fate of a chemical reaction associated with an index-two saddle

Nagahata

Teramoto

et al. 2013

Phys. Rev. E

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Reactivity boundaries that divide the destination and the origin of trajectories are of crucial importance to reveal the mechanism of reactions. We investigate whether such reactivity boundaries can be extracted for higher index saddles in terms of a nonlinear canonical transformation successful for index-one saddles by using a model system with an index-two saddle. It is found that the true reactivity boundaries do not coincide with those extracted by the transformation taking into account a nonlinearity in the region of the saddle even for small perturbations, and the discrepancy is more pronounced for the less repulsive direction of the index-two saddle system. The present result indicates an importance of the global properties of the phase space to identify the reactivity boundaries, relevant to the question of what reactant and product are in phase space, for saddles with index more than one. Saddle points and the dynamics in their vicinities play crucial roles in chemical reactions. A saddle point on a multidimensional potential energy surface is defined as a stationary point at which the Hessian matrix does not have zero eigenvalues and, at least, one of the eigenvalues is negative. Saddle points are classified by the number of the negative eigenvalues, and a saddle that has n negative eigenvalues is called an index-n saddle. An index-one saddle on a potential surface has especially long been considered to make a bottleneck for reactions [1][2][3], the sole unstable direction corresponding to the "reaction coordinate." This is because index-one saddles are considered to be the lowest energy stationary point connecting two potential minima, of which one corresponds to the reactant and the other to the product, and the system must traverse the index-one saddle from the reactant to the product [4][5][6][7].To estimate reaction rate constants across the saddles, transition state theory was proposed [1][2][3], by envisaging the existence of a nonrecrossing dividing surface [i.e., transition state (TS)] in the region of an index-one saddle. Recent studies of nonlinear dynamics in the vicinity of index-one saddles have revealed the firm theoretical ground for the robust existence of the no-return TS in the phase space [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] (see also Refs. [25,26], and references therein). and systems with rovibrational couplings [18,19] and showed the robust existence of reaction boundaries even while a no-return TS ceases to exist [13].For complex molecular systems, the potential energy surface becomes more complicated, and transitions from a potential basin to another involve not only index-one saddles but also higher index saddles [28][29][30]. For example, it was shown in a computer simulation of an inert gas cluster containing seven atoms that transitions from a solid-like phase to a liquid-like phase occur mostly through index-two saddles rather than through index-one saddle with the increase of kinetic temperature [29]. This indicates that the more rugged a ...

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Section: Pechukas and Pollakmentioning

confidence: 99%

“…Chemical reactions associated with index-two saddles were also reported in several molecular systems [57][58][59][60][61][62][63] by using several searching algorithms (section 6.3 p. 298 of Ref. 64 and references therein).…”

Section: Pechukas and Pollakmentioning

confidence: 99%

Reactivity boundaries to separate the fate of a chemical reaction associated with an index-two saddle

Nagahata

Teramoto

et al. 2013

Phys. Rev. E

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“…For complex systems, the potential energy surface becomes more complicated, and transitions from a potential basin to another involve not only index 1 saddles but also higher-index saddles [56][57][58][59][60][61][62][63][64]. Recently, the role of index 2 saddles revealed several dynamical aspects.…”

Section: Introductionmentioning

confidence: 99%

“…Chemical reactions associated with index 2 saddles were also reported in several molecular systems [58][59][60][61][62][63][64] by using several searching algorithms (section 6.3, p. 298, of Ref. [65] and references therein).…”

Section: Introductionmentioning

confidence: 99%

“…Note, however, that it is not necessary for the highest energy point on the minimum energy path between two potential minima to be an index 1 saddle [67]. Moreover, one can still find many studies such as aminoborane [58], PF 3 [58], NH 5 [59], NF 2 H 3 [60], water dimer [61,62], H 5 + [63], and H 2 CO [64] that identify a variety of index 2 saddles in molecular isomerization reactions.…”

Section: Introductionmentioning

confidence: 99%

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Reactivity boundaries for chemical reactions associated with higher-index and multiple saddles

Nagahata

Teramoto

et al. 2013

Phys. Rev. E

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Reactivity boundaries that divide the origin and destination of trajectories are of crucial importance to reveal the mechanism of reactions, which was recently found to exist robustly even at high energies for index 1 saddles [Phys. Rev. Lett. 105, 048304 (2010)]. Here we revisit the concept of the reactivity boundary and propose a more general definition that can involve a single reaction associated with a bottleneck composed of higher-index saddles and/or several saddle points with different indices, where the normal form theory, based on expansion around a single stationary point, does not work. We numerically demonstrate the reactivity boundary by using a reduced model system of the H 5 + cation where the proton exchange reaction takes place through a bottleneck composed of two index 2 saddle points and two index 1 saddle points. The cross section of the reactivity boundary in the reactant region of the phase space reveals which initial conditions are effective in making the reaction happen and thus sheds light on the reaction mechanism.

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E−Z Isomerization in Guanidine: Second‐order Saddle Dynamics, Non‐statisticality, and Time‐frequency Analysis

et al. 2022

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Our recent work on the EÀ Z isomerization reaction of guanidine using ab initio chemical dynamics simulations [Rashmi et al., Regul. Chaotic Dyn. 2021, 26, 119] emphasized the role of second-order saddle (SOS) in the isomerization reaction; however, we could not unequivocally establish the nonstatistical nature of the dynamics followed in the reaction. In the present study, we performed thousands of on-the-fly trajectories using forces computed at the MNDO level to investigate the influence of second-order saddle in the EÀ Z isomerization reaction of guanidine and the role of intramolecular vibrational energy redistribution (IVR) on the reaction dynamics. The simulations reveal that while majority of the trajectories follow the traditional transition state pathways, 15 % of the trajectories follow the SOS path. The dynamics was found to be highly non-statistical with the survival probabilities of the reactants showing large deviations from those obtained within the RRKM assumptions. In addition, a detailed analysis of the dynamics using time-dependent frequencies and the frequency ratio spaces reveal the existence of multiple resonance junctions that indicate the existence of regular dynamics and long-lived quasi-periodic trajectories in the phase space associated with non-RRKM behavior.

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Study of the structural and thermodynamic stability of pentacoordinated nitrogen compounds NF2X3 (X = H, Cl, Br): Ab initio calculations

Cited by 9 publications

References 19 publications

Reactivity boundaries to separate the fate of a chemical reaction associated with an index-two saddle

Reactivity boundaries to separate the fate of a chemical reaction associated with an index-two saddle

Reactivity boundaries for chemical reactions associated with higher-index and multiple saddles

E−Z Isomerization in Guanidine: Second‐order Saddle Dynamics, Non‐statisticality, and Time‐frequency Analysis

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