The Experts below are selected from a list of 167430 Experts worldwide ranked by ideXlab platform
Joel M Bowman - One of the best experts on this subject based on the ideXlab platform.
-
a new multi reference configuration interaction Potential Energy Surface for h2co and preliminary studies of roaming
Philosophical Transactions of the Royal Society A, 2017Co-Authors: Xiaohong Wang, P L Houston, Joel M BowmanAbstract:We report a new global Potential Energy Surface (PES) for H2CO, based on precise fitting of roughly 67000 MRCI/cc-pVTZ energies. This PES describes the global minimum, the cis- and trans-HCOH isome...
-
communication a chemically accurate global Potential Energy Surface for the ho co h co2 reaction
Journal of Chemical Physics, 2012Co-Authors: Yimin Wang, Dai Qian Xie, Joel M Bowman, Bin Jiang, Richard Dawes, Hua GuoAbstract:We report a chemically accurate global Potential Energy Surface for the HOCO system based on high-level ab initio calculations at ∼35 000 points. The Potential Energy Surface is shown to reproduce important stationary points and minimum Energy paths. Quasi-classical trajectory calculations indicated a good agreement with experimental data.
-
Potential Energy Surface and multimode vibrational analysis of c2h3
Journal of Chemical Physics, 2006Co-Authors: Amit Sharma, Bastiaan J Braams, Stuart Carter, Ralf Schneider, Ben Shepler, Joel M BowmanAbstract:A full dimensional, ab initio-based semiglobal Potential Energy Surface for C2H3+ is reported. The ab initio electronic energies for this molecule are calculated using the spin-restricted, coupled cluster method restricted to single and double excitations with triples corrections [RCCSD(T)]. The RCCSD(T) method is used with the correlation-consistent polarized valence triple-zeta basis augmented with diffuse functions (aug-cc-pVTZ). The ab initio Potential Energy Surface is represented by a many-body (cluster) expansion, each term of which uses functions that are fully invariant under permutations of like nuclei. The fitted Potential Energy Surface is validated by comparing normal mode frequencies at the global minimum and secondary minimum with previous and new direct ab initio frequencies. The Potential Surface is used in vibrational analysis using the “single-reference” and “reaction-path” versions of the code MULTIMODE.
-
ab initio global Potential Energy Surface for h5 h3 h2
Journal of Chemical Physics, 2005Co-Authors: Zhen Xie, Bastiaan J Braams, Joel M BowmanAbstract:An accurate global Potential-Energy Surface (PES) is reported for H5(+) based on more than 100,000 CCSD(T)/aug-cc-pVTZ ab initio energies. This PES has full permutational symmetry with respect to interchange of H atoms and dissociates to H3(+) and H2. Ten known stationary points of H5(+) are characterized and compared to previous ab initio calculations. Quantum diffusion Monte Carlo calculations are performed on the PES to obtain the zero-point Energy of H5(+) and the anharmonic dissociation Energy (D0) of H5(+) --> H3(+) + H2. The rigorous zero-point state of H4D+ is also calculated and discussed within the context of a strictly classical approach to obtain the branching ratio of the reaction H4D+ --> H3(+) + HD and H2D+ + H2. Such an approach is taken using the PES and critiqued based on the properties of the quantum zero-point state. Finally, a simple procedure for adding the long range-interaction Energy is described.
-
full dimensional vibrational calculations for h5o2 using an ab initio Potential Energy Surface
Journal of Chemical Physics, 2005Co-Authors: Anne B Mccoy, Stuart Carter, Xinchuan Huang, Marc Y Landeweer, Joel M BowmanAbstract:We report quantum diffusion Monte Carlo (DMC) and variational calculations in full dimensionality for selected vibrational states of H(5)O(2) (+) using a new ab initio Potential Energy Surface [X. Huang, B. Braams, and J. M. Bowman, J. Chem. Phys. 122, 044308 (2005)]. The Energy and properties of the zero-point state are focused on in the rigorous DMC calculations. OH-stretch fundamentals are also calculated using "fixed-node" DMC calculations and variationally using two versions of the code MULTIMODE. These results are compared with infrared multiphoton dissociation measurements of Yeh et al. [L. I. Yeh, M. Okumura, J. D. Myers, J. M. Price, and Y. T. Lee, J. Chem. Phys. 91, 7319 (1989)]. Some preliminary results for the energies of several modes of the shared hydrogen are also reported.
Hua Guo - One of the best experts on this subject based on the ideXlab platform.
-
many body permutationally invariant polynomial neural network Potential Energy Surface for n4
Journal of Chemical Theory and Computation, 2020Co-Authors: Zoltán Varga, Donald G Truhlar, Hua GuoAbstract:A Potential Energy Surface (PES) for high-Energy collisions between nitrogen molecules is useful for modeling chemical dynamics in shock waves and plasmas. In the present work, we fit the many-body...
-
kinetics and dynamics of the c 3p h2o reaction on a full dimensional accurate triplet state Potential Energy Surface
Physical Chemistry Chemical Physics, 2017Co-Authors: Changjian Xie, Hua GuoAbstract:Correction for 'Kinetics and dynamics of the C(3P) + H2O reaction on a full-dimensional accurate triplet state Potential Energy Surface' by Jun Li et al., Phys. Chem. Chem. Phys., 2017, 19, 23280-23288.
-
an accurate multi channel multi reference full dimensional global Potential Energy Surface for the lowest triplet state of h2o2
Physical Chemistry Chemical Physics, 2016Co-Authors: Richard Dawes, Hua GuoAbstract:The lowest triplet state of the H2O2 system features multiple reaction channels, including several relevant to the combustion of H2. To accurately map out the global Potential Energy Surface, ∼28 000 geometries were sampled over a large configuration space including all important asymptotes, and electronic energies at these points were calculated at the level of the explicitly correlated version of the multi-reference configuration interaction (MRCI-F12) method. A new multi-channel global Potential Energy Surface was constructed by fitting the ab initio data set using a permutation invariant polynomial-neural network method, resulting in a total root mean square fitting error of only 6.7 meV (0.15 kcal mol−1). Various kinetics and dynamical properties of several relevant reactions were calculated on the new MRCI Potential Energy Surface, and compared with the available experimental results.
-
communication a chemically accurate global Potential Energy Surface for the ho co h co2 reaction
Journal of Chemical Physics, 2012Co-Authors: Yimin Wang, Dai Qian Xie, Joel M Bowman, Bin Jiang, Richard Dawes, Hua GuoAbstract:We report a chemically accurate global Potential Energy Surface for the HOCO system based on high-level ab initio calculations at ∼35 000 points. The Potential Energy Surface is shown to reproduce important stationary points and minimum Energy paths. Quasi-classical trajectory calculations indicated a good agreement with experimental data.
-
a global ab initio Potential Energy Surface for hno a3a and quantum mechanical studies of vibrational states and reaction dynamics
Journal of Chemical Physics, 2011Co-Authors: Changjian Xie, Dai Qian Xie, Hua GuoAbstract:A new global Potential Energy Surface for the lowest triplet electronic state (a3A″) of HNO has been developed by a three-dimensional cubic spline interpolation of more than 13 000 ab initio points, which were calculated at the multireference configuration interaction level with Davidson correction using the augmented correlation-consistent polarized valence quintuple zeta basis set. Two minima and five saddle points were found on the Potential Energy Surface. Low-lying vibrational states were obtained in this new Potential using the Lanczos method and assigned. In addition, thermal rate constants for the N + OH → H + NO reactions were obtained using an exact wave packet method. Reasonably good agreement with experimental data was obtained.
A J C Varandas - One of the best experts on this subject based on the ideXlab platform.
-
accurate chipr Potential Energy Surface for the lowest triplet state of c3
Journal of Physical Chemistry A, 2019Co-Authors: Carlos Frederico Duarte Rocha, A J C VarandasAbstract:We report the first global ab initio-based Potential Energy Surface (PES) for ground-state triplet C3(3A′) based on accurate energies extrapolated to the complete basis set (CBS) limit, and using t...
-
accurate adiabatic Potential Energy Surface for 12a state of fh2 based on ab initio data extrapolated to the complete basis set limit
European Physical Journal D, 2015Co-Authors: Yuzhi Song, A J C VarandasAbstract:An accurate single-sheeted double many-body expansion Potential Energy Surface is reported for the title system. It is obtained by using the aug-cc-pVTZ and aug-cc-pVQZ basis sets with extrapolation of the electron correlation Energy to the complete basis set limit, plus extrapolation to the complete basis set limit of the complete-active-space self-consistent field Energy. The collinear and bending barrier heights of the new global Potential Energy Surface is 2.301 and 1.768 kcal mol-1, in very good agreement with the values of 2.222 and 1.770 kcal mol-1 from the current best Potential Energy Surface. In particular, the new Potential Energy Surface describes well the important van der Waals interactions which is very useful for investigating the dynamics of the title system. Thus, the new Potential Energy Surface can both be recommended for dynamics studies of the F + H2 reaction and as building block for constructing the Potential Energy Surfaces of larger fluorine/hydrogen containing systems. Based on the new Potential Energy Surface, a preliminary theoretical study of the reaction F(2P) + H2 (X1 Σ g +) → FH(X 1 Σ +) + H(2S) has been carried out with the methods of quasi-classical trajectory and quantum mechanical. The results have shown that the new PES is suitable for any kind of dynamics studies.
-
accurate Potential Energy Surface for the 12a state of nh2 scaling of external correlation versus extrapolation to the complete basis set limit
Journal of Physical Chemistry A, 2010Co-Authors: A J C VarandasAbstract:An accurate single-sheeted double many-body expansion Potential Energy Surface is reported for the title system which is suitable for dynamics and kinetics studies of the reactions of N(2D) + H2(X1Σg+) ⇌ NH(a1Δ) + H(2S) and their isotopomeric variants. It is obtained by fitting ab initio energies calculated at the multireference configuration interaction level with the aug-cc-pVQZ basis set, after slightly correcting semiempirically the dynamical correlation using the double many-body expansion-scaled external correlation method. The function so obtained is compared in detail with a Potential Energy Surface of the same family obtained by extrapolating the calculated raw energies to the complete basis set limit. The topographical features of the novel global Potential Energy Surface are examined in detail and found to be in general good agreement with those calculated directly from the raw ab initio energies, as well as previous calculations available in the literature. The novel function has been built so...
-
single valued dmbe Potential Energy Surface for hso a distributed n body polynomial approach
Journal of Physical Chemistry A, 2001Co-Authors: Emilio Martineznunez, A J C VarandasAbstract:An accurate single-valued double many-body expansion (DMBE) Potential Energy Surface is reported for the ground electronic state of HSO based on novel MR CISD ab initio energies suitably corrected for the complete one-electron basis set/complete CI limit. To improve the accuracy of the fit, we have suggested a n-body distributed polynomial approach which implies using individual multinomial developments at the various stationary points. For simplicity, only the three most relevant such points have been considered: two minima (HSO, HOS) and the saddle point connecting them.
Mengtao Sun - One of the best experts on this subject based on the ideXlab platform.
-
accurate ab initio based adiabatic global Potential Energy Surface for the 22a state of nh2 by extrapolation to the complete basis set limit
Journal of Chemical Physics, 2013Co-Authors: Mengtao SunAbstract:A full three-dimensional global Potential Energy Surface is reported first time for the title system, which is important for the photodissociation processes. It is obtained using double many-body expansion theory and an extensive set of accurate ab initio energies extrapolated to the complete basis set limit. Such a work can be recommended for dynamics studies of the N(2D) + H2 reaction, a reliable theoretical treatment of the photodissociation dynamics and as building blocks for constructing the double many-body expansion Potential Energy Surface of larger nitrogen/hydrogen containing systems. In turn, a preliminary theoretical study of the reaction N(D2)+H2(X1Σg+)(ν=0,j=0)→ NH (a1Δ)+H(S2) has been carried out with the method of quasi-classical trajectory on the new Potential Energy Surface. Integral cross sections and thermal rate constants have been calculated, providing perhaps the most reliable estimate of the integral cross sections and the rate constants known thus far for such a reaction.
-
accurate double many body expansion Potential Energy Surface by extrapolation to the complete basis set limit and dynamics calculations for ground state of nh2
Journal of Computational Chemistry, 2013Co-Authors: Jiuchuang Yuan, Maodu Chen, Mengtao SunAbstract:An accurate single-sheeted double many-body expansion Potential Energy Surface is reported for the title system. A switching function formalism has been used to warrant the correct behavior at the H2(X1 sigma g+)+N(2D) and NH(X3 sigma-)+H(2S) dissociation channels involving nitrogen in the ground N(4S) and first excited N(2D) states. The topographical features of the novel global Potential Energy Surface are examined in detail, and found to be in good agreement with those calculated directly from the raw ab initio energies, as well as previous calculations available in the literature. The novel Surface can be using to treat well the Renner-Teller degeneracy of the 12A and 12A states of NH2. Such a work can both be recommended for dynamics studies of the N(2D)+H2 reaction and as building blocks for constructing the double many-body expansion Potential Energy Surface of larger nitrogen/hydrogen-containing systems. In turn, a test theoretical study of the reaction N(2D)+H2(X1 sigma g+)(=0,j=0)NH(X3 sigma-)+H(2S) has been carried out with the method of quantum wave packet on the new Potential Energy Surface. Reaction probabilities, integral cross sections, and differential cross sections have been calculated. Threshold exists because of the Energy barrier (68.5 meV) along the minimum Energy path. On the curve of reaction probability for total angular momentum J=0, there are two sharp peaks just above threshold. The value of integral cross section increases quickly from zero to maximum with the increase of collision Energy, and then stays stable with small oscillations. The differential cross section result shows that the reaction is a typical forward and backward scatter in agreement with experimental measurement result. (c) 2013 Wiley Periodicals, Inc.
-
Ab initio-based double many-body expansion Potential Energy Surface for the first excited triplet state of the ammonia molecule.
The Journal of chemical physics, 2012Co-Authors: Yuzhi Song, P. Song, Yong Ding, Mengtao SunAbstract:A global single-sheeted double many-body expansion Potential Energy Surface is reported for the first excited triplet state of NH 3. It employs an approximate cluster expansion of the molecular Potential that utilizes previously reported functions of the same family for the triatomic fragments. Four-body Energy terms have been calibrated from extensive accurate ab initio data so as to reproduce the main features of the title system. A new switching function formalism has been reported to approximate the true multisheeted nature of NH 3(A2′′3) Potential Energy Surface, thus allowing the correct behavior at the NH2(2A″) + H(2S) and NH2(4A″) + H(2S) dissociation limits. The resulting fully six-dimensional Potential Energy function reproduces the correct symmetry under the permutation of identical atoms, and predicts the correct behavior at all dissociation channels while providing a realistic representation at all interatomic separations. The major attributes of the NH 3 double many-body expansion Potential ...
Dominic J. Wales - One of the best experts on this subject based on the ideXlab platform.
-
research papera stress tensor eigenvector projection space for the h2o 5 Potential Energy Surface
Chemical Physics Letters, 2017Co-Authors: Tianlv Xu, James D Farrell, Roya Momen, Samantha Jenkins, Alireza Azizi, Steven R Kirk, Dominic J. WalesAbstract:A stress tensor eigenvector projection space is created to describe reaction pathways on the (H2O)5 MP2 Potential Energy Surface. Evidence for the stabilizing role of the O---O bonding interactions is found from the length of the recently introduced stress tensor trajectory in the stress tensor eigenvector projection space. The stress tensor trajectories demonstrate coupling behavior of the adjoining covalent (σ) O-H and hydrogen bonds due to sharing of covalent character. Additionally, the stress tensor trajectories can show dynamic coupling effects of pairs of σ bonds and of pairs of hydrogen bonds.
-
a stress tensor eigenvector projection space for the h 2 o 5 Potential Energy Surface
Chemical Physics Letters, 2017Co-Authors: Tianlv Xu, James D Farrell, Roya Momen, Samantha Jenkins, Alireza Azizi, Steven R Kirk, Dominic J. WalesAbstract:Abstract A stress tensor eigenvector projection space is created to describe reaction pathways on the (H 2 O) 5 MP2 Potential Energy Surface. Evidence for the stabilizing role of the O---O bonding interactions is found from the length of the recently introduced stress tensor trajectory in the stress tensor eigenvector projection space. The stress tensor trajectories demonstrate coupling behavior of the adjoining covalent (σ) O-H and hydrogen bonds due to sharing of covalent character. Additionally, the stress tensor trajectories can show dynamic coupling effects of pairs of σ bonds and of pairs of hydrogen bonds.