Browsing QF-Artigos by Author "3c5d6234-c067-40ff-9d56-29b3ba5031a6"
Now showing items 1-20 of 23
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Ab initio investigation of the H2O2 + F elementary reaction
Bahri, H.; Bahri, M.; Fernández Ramos, Antonio (Elsevier, 2016-07-01) -
Accounting for conformational flexibility and torsional anharmonicity in the H + CH3CH2OH hydrogen abstraction reactions: A multi-path variational transition state theory study
Meana Pañeda, Rubén; Fernández Ramos, Antonio (AIP Publishing, 2014-05-06)This work reports a detailed theoretical study of the hydrogen abstraction reactions from ethanol by atomic hydrogen. The calculated thermal rate constants take into account torsional anharmonicity and conformational ... -
Accurate treatment of two-dimensional non-separable hindered internal rotors
Fernández Ramos, Antonio (AIP Publishing, 2013-04-04)This work presents an accurate way for calculating partition functions of strongly coupled hindered rotors in two dimensions. The two-dimensional torsional potential is generated from electronic structure calculations and ... -
Anharmonicity of Coupled Torsions: The Extended Two-Dimensional Torsion Method and Its Use To Assess More Approximate Methods
Simón Carballido, Luis; Bao, Junwei Lucas; Alves, Tiago Vinicius; Meana Pañeda, Rubén; Truhlar, Donald G.; Fernández Ramos, Antonio (American Chemical Society, 2017-06-30)In this work we present the extended two-dimensional torsion (E2DT) method and use it to analyze the performance of several methods that incorporate torsional anharmonicity more approximately for calculating rotational–vibrational ... -
Calculation of the two-dimensional non-separable partition function for two molecular systems
Simón-Carballido, Luis; Fernández-Ramos, Antonio (Springer, 2014-04-02)We present the application of an accurate quantum treatment, called two-dimensional non-separable (2D-NS), to the calculation of internal rotation partition functions of molecules with two rotors. This methodology involves ... -
A Combined Systematic-Stochastic Algorithm for the Conformational Search in Flexible Acyclic Molecules
Ferro Costas, David; Fernández Ramos, Antonio (Frontiers, 2020)We propose an algorithm that is a combination of systematic variation of the torsions and Monte Carlo (or stochastic) search. It starts with a trial geometry in internal coordinates and with a set of preconditioned torsional ... -
Communication: Selection rules for tunneling splitting of vibrationally excited levels
Siebrand, Willem; Smedarchina, Zorka; Fernández-Ramos, Antonio (AIP Publishing, 2013-07-08)Five symmetry-based selection rules are formulated that relate the tunneling splitting of a vibrationally excited level to that of the ground level in molecules with a symmetric double-minimum potential. The rules, which ... -
Correct Interpretation of How Tunneling Proceeds at Low Temperatures in the Proton Transfer Reactions Involving Thiotropolone: A Comment
Fernández-Ramos, Antonio (Wiley, 2013-07-05)The correct interpretation is provided of how tunneling proceeds at low temperatures in the proton transfer Reactions (1) and (3) involving thiotropolone and tropolone (see the Arrhenius plots). It is also shown that the ... -
Entanglement and co-tunneling of two equivalent protons in hydrogen bond pairs
Smedarchina, Zorka; Siebrand, Willem; Fernández-Ramos, Antonio (AIP Publishing, 2018)A theoretical study is reported of a system of two identical symmetric hydrogen bonds, weakly coupled such that the two mobile protons can move either separately (stepwise) or together (concerted). It is modeled by two ... -
Hindered rotor tunneling splittings: an application of the two-dimensional non-separable method to benzyl alcohol and two of its fluorine derivatives
Alves, Tiago Vinicius; Simón-Carballido, Luis; Rei Ornellas, Fernando; Fernández-Ramos, Antonio (Royal Society of Chemistry, 2016-02-29)In this work we present a novel application of the two-dimensional non-separable (2D-NS) method to the calculation of torsional tunneling splittings in systems with two hindered internal rotors. This method could be ... -
Influence of Multiple Conformations and Paths on Rate Constants and Product Branching Ratios. Thermal Decomposition of 1-Propanol Radicals
Ferro Costas, David; Martínez Núñez, Emilio; Rodríguez Otero, Jesús; Cabaleiro Lago, Enrique Manuel; Estévez, Carlos M.; Fernández Rodríguez, Berta; Fernández Ramos, Antonio; Vázquez Rodríguez, Saulo Angel (American Chemical Society, 2018-05-15)The potential energy surface involved in the thermal decomposition of 1-propanol radicals was investigated in detail using automated codes (tsscds2018 and Q2DTor). From the predicted elementary reactions, a relevant reaction ... -
Kinetic Isotope Effects in Multipath VTST: Application to a Hydrogen Abstraction Reaction
Simón-Carballido, Luis; Alves, Tiago Vinicius; Dybala-Defratyka, Agnieszka; Fernández-Ramos, Antonio (American Chemical Society, 2016)In this work we apply multipath canonical variational transition state theory with small-tunneling corrections (MP-CVT/SCT) to the hydrogen abstraction reaction from ethanol by atomic hydrogen in aqueous solution at room ... -
Kinetics of the Methanol Reaction with OH at Interstellar, Atmospheric, and Combustion Temperatures
Gao, Lu Gem; Zheng, Jingjing; Fernández-Ramos, Antonio; Truhlar, Donald G.; Xu, Xuefei (American Chemical Society, 2018-01-04)The OH radical is the most important radical in combustion and in the atmosphere, and methanol is a fuel and antifreeze additive, model biofuel, and trace atmospheric constituent. These reagents are also present in ... -
Methanol dimer formation drastically enhances hydrogen abstraction from methanol by OH at low temperature
Siebrand, Willem; Smedarchina, Zorka; Martínez Núñez, Emilio; Fernández-Ramos, Antonio (Royal Society of Chemistry, 2016-07-22)The kinetics of the reaction of methanol with hydroxyl radicals is revisited in light of the reported new kinetic data, measured in cold expansion beams. The rate constants exhibit an approximately 102-fold increase when ... -
Multidimensional Hamiltonian for tunneling with position-dependent mass
Fernández-Ramos, Antonio; Smedarchina, Zorka; Siebrand, Willem (APS Physics, 2014-09-15)A multidimensional Hamiltonian for tunneling is formulated, based on the mode with imaginary frequency of the transition state as a reaction coordinate. To prepare it for diagonalization, it is transformed into a lower-dimension ... -
New interpretation of proton and deuteron tunneling in 2'-methylacetophenone
Fernández-Ramos, Antonio; Siebrand, Willem; Smedarchina, Zorka (Elsevier, 2013-10-24)The enol–keto transition rate constants in 2′-methylacetophenone observed by Grellmann et al. are calculated from first principles. The results reinterpret the proposed mechanism and show that proton tunneling is preceded ... -
Reply to the ‘Comment on “Methanol dimer formation drastically enhances hydrogen abstraction from methanol by OH at low temperature”’ by D. Heard, R. Shannon, J. Gomez Martin, R. Caravan, M. Blitz, J. Plane, M. Antiñolo, M. Agundez, E. Jimenez, B. Ballesteros, A. Canosa, G. El Dib, J. Albaladejo and J. Cernicharo, Phys. Chem. Chem. Phys., 2018, 20, DOI: 10.1039/C7CP04561A
Siebrand, Willem; Smedarchina, Zorka; Ferro Costas, David; Martínez Núñez, Emilio; Fernández Ramos, Antonio (Royal Society of Chemistry, 2018-02-22)In this Reply we answer the two main arguments raised in the Comment. The first argument is related to the binding energy of the methanol dimer and its influence on the dimerization rate constant. We show that the dimerization ... -
Role of Microsolvation and Quantum Effects in the Accurate Prediction of Kinetic Isotope Effects: The Case of Hydrogen Atom Abstraction in Ethanol by Atomic Hydrogen in Aqueous Solution
Kannath, Suraj; Adamczyk, Paweł; Ferro Costas, David; Fernández Ramos, Antonio; Major, Dan Thomas; Dybała-Defratyka, Agnieszka (American Chemical Society, 2020)Hydrogen abstraction from ethanol by atomic hydrogen in aqueous solution is studied using two theoretical approaches: the multipath variational transition state theory (MP-VTST) and a path-integral formalism in combination ... -
The rainbow instanton method: A new approach to tunneling splitting in polyatomics
Smedarchina, Zorka; Siebrand, Willem; Fernández-Ramos, Antonio (AIP Publishing, 2012-12-11)A new instanton approach is reported to tunneling at zero-temperature in multidimensional (MD) systems in which a “light particle” is transferred between two equivalent “heavy” sites. The method is based on two concepts. ... -
Theoretical Kinetics Study of the F(2P) + NH3 Hydrogen Abstraction Reaction
Espinosa-García, Joaquín; Fernández-Ramos, Antonio; Suleimanov, Y. V.; Corchado, J.C. (American Chemical Society, 2014-01-02)The hydrogen abstraction reaction of fluorine with ammonia represents a true chemical challenge because it is very fast, is followed by secondary abstraction reactions, which are also extremely fast, and presents an ...