The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
R Sayos - One of the best experts on this subject based on the ideXlab platform.
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an Analytical Representation of the ground potential energy surface 2a of the h cl2 hcl cl and cl hcl hcl cl reactions based on ab initio calculations
Journal of Chemical Physics, 1998Co-Authors: Miguel Gonzalez, J Hijazo, Juan J Novoa, R SayosAbstract:In this work we have studied at an ab initio level the lowest 2A′ potential energy surface (PES) of the HCl2 system. This PES is involved in the H(2S)+Cl2(X 1Σg+)→HCl(X 1Σ+)+Cl(2P) and Cl(2P)+HCl(X 1Σ+)→HCl(X 1Σ+)+Cl(2P) gas phase elementary chemical reactions. The former reaction is an important chemical laser while the second one is the most frequently used prototype of heavy–light–heavy reaction. A large number of points on the 2A′ PES have been calculated at the PUMP2/6-311G(3d2 f,3p2d) ab initio level. The ab initio calculations show the existence of two angular transition states with negligible or very small barriers to collinearity. This and other properties of the PES are in agreement with previous studies. An Analytical expression based on a many-body expansion has been used to obtain a satisfactory fit of the 740 ab initio points calculated, with a root-mean-square deviation within the range of the estimated ab initio method error margin. This Analytical Representation of the 2A′ PES has been us...
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An Analytical Representation of the ground potential energy surface (2A′) of the H+Cl2→HCl+Cl and Cl+HCl→HCl+Cl reactions, based on ab initio calculations
Journal of Chemical Physics, 1998Co-Authors: Miguel Gonzalez, J Hijazo, Juan J Novoa, R SayosAbstract:In this work we have studied at an ab initio level the lowest 2A′ potential energy surface (PES) of the HCl2 system. This PES is involved in the H(2S)+Cl2(X 1Σg+)→HCl(X 1Σ+)+Cl(2P) and Cl(2P)+HCl(X 1Σ+)→HCl(X 1Σ+)+Cl(2P) gas phase elementary chemical reactions. The former reaction is an important chemical laser while the second one is the most frequently used prototype of heavy–light–heavy reaction. A large number of points on the 2A′ PES have been calculated at the PUMP2/6-311G(3d2 f,3p2d) ab initio level. The ab initio calculations show the existence of two angular transition states with negligible or very small barriers to collinearity. This and other properties of the PES are in agreement with previous studies. An Analytical expression based on a many-body expansion has been used to obtain a satisfactory fit of the 740 ab initio points calculated, with a root-mean-square deviation within the range of the estimated ab initio method error margin. This Analytical Representation of the 2A′ PES has been us...
Elizabeth M Meiering - One of the best experts on this subject based on the ideXlab platform.
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On the Analytical Representation of free energy profiles with a Morse/long-range model: Application to the water dimer
Journal of Chemical Physics, 2013Co-Authors: Yalina Tritzant-martinez, Tao Zeng, Aron Broom, Elizabeth M MeieringAbstract:We investigate the Analytical Representation of potentials of mean force (pmf) using the Morse/long-range (MLR) potential approach. The MLR method had previously been used to represent potential energy surfaces, and we assess its validity for representing free-energies. The advantage of the approach is that the potential of mean force data only needs to be calculated in the short to medium range region of the reaction coordinate while the long range can be handled Analytically. This can result in significant savings in terms of computational effort since one does not need to cover the whole range of the reaction coordinate during simulations. The water dimer with rigid monomers whose interactions are described by the commonly used TIP4P model [W. Jorgensen and J. Madura, Mol. Phys. 56, 1381 (1985)]10.1080/00268978500103111 is used as a test case. We first calculate an “exact” pmf using direct Monte Carlo (MC) integration and term such a calculation as our gold standard (GS). Second, we compare this GS wit...
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on the Analytical Representation of free energy profiles with a morse long range model application to the water dimer
Journal of Chemical Physics, 2013Co-Authors: Yalina Tritzantmartinez, Tao Zeng, Aron Broom, Elizabeth M MeieringAbstract:We investigate the Analytical Representation of potentials of mean force (pmf) using the Morse/long-range (MLR) potential approach. The MLR method had previously been used to represent potential energy surfaces, and we assess its validity for representing free-energies. The advantage of the approach is that the potential of mean force data only needs to be calculated in the short to medium range region of the reaction coordinate while the long range can be handled Analytically. This can result in significant savings in terms of computational effort since one does not need to cover the whole range of the reaction coordinate during simulations. The water dimer with rigid monomers whose interactions are described by the commonly used TIP4P model [W. Jorgensen and J. Madura, Mol. Phys. 56, 1381 (1985)]10.1080/00268978500103111 is used as a test case. We first calculate an “exact” pmf using direct Monte Carlo (MC) integration and term such a calculation as our gold standard (GS). Second, we compare this GS wit...
Miguel Gonzalez - One of the best experts on this subject based on the ideXlab platform.
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an Analytical Representation of the ground potential energy surface 2a of the h cl2 hcl cl and cl hcl hcl cl reactions based on ab initio calculations
Journal of Chemical Physics, 1998Co-Authors: Miguel Gonzalez, J Hijazo, Juan J Novoa, R SayosAbstract:In this work we have studied at an ab initio level the lowest 2A′ potential energy surface (PES) of the HCl2 system. This PES is involved in the H(2S)+Cl2(X 1Σg+)→HCl(X 1Σ+)+Cl(2P) and Cl(2P)+HCl(X 1Σ+)→HCl(X 1Σ+)+Cl(2P) gas phase elementary chemical reactions. The former reaction is an important chemical laser while the second one is the most frequently used prototype of heavy–light–heavy reaction. A large number of points on the 2A′ PES have been calculated at the PUMP2/6-311G(3d2 f,3p2d) ab initio level. The ab initio calculations show the existence of two angular transition states with negligible or very small barriers to collinearity. This and other properties of the PES are in agreement with previous studies. An Analytical expression based on a many-body expansion has been used to obtain a satisfactory fit of the 740 ab initio points calculated, with a root-mean-square deviation within the range of the estimated ab initio method error margin. This Analytical Representation of the 2A′ PES has been us...
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An Analytical Representation of the ground potential energy surface (2A′) of the H+Cl2→HCl+Cl and Cl+HCl→HCl+Cl reactions, based on ab initio calculations
Journal of Chemical Physics, 1998Co-Authors: Miguel Gonzalez, J Hijazo, Juan J Novoa, R SayosAbstract:In this work we have studied at an ab initio level the lowest 2A′ potential energy surface (PES) of the HCl2 system. This PES is involved in the H(2S)+Cl2(X 1Σg+)→HCl(X 1Σ+)+Cl(2P) and Cl(2P)+HCl(X 1Σ+)→HCl(X 1Σ+)+Cl(2P) gas phase elementary chemical reactions. The former reaction is an important chemical laser while the second one is the most frequently used prototype of heavy–light–heavy reaction. A large number of points on the 2A′ PES have been calculated at the PUMP2/6-311G(3d2 f,3p2d) ab initio level. The ab initio calculations show the existence of two angular transition states with negligible or very small barriers to collinearity. This and other properties of the PES are in agreement with previous studies. An Analytical expression based on a many-body expansion has been used to obtain a satisfactory fit of the 740 ab initio points calculated, with a root-mean-square deviation within the range of the estimated ab initio method error margin. This Analytical Representation of the 2A′ PES has been us...
Roberto Marquardt - One of the best experts on this subject based on the ideXlab platform.
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a global Analytical Representation of the potential energy surface of the fhf anion
Journal of Physical Chemistry A, 2016Co-Authors: Yann Cornaton, Roberto MarquardtAbstract:A global Analytical Representation of the potential energy hypersurface of the lowest adiabatic electronic state of the FHF– anion is derived from ab initio calculations at the coupled cluster level of theory with full single and double and perturbative triple excitations using explicitly correlated atomic basis functions. The new compact function of interatomic distances combines covalent short-range and long-range electrostatic interaction forms and assesses accurately both the lowest reaction channels between the F– and HF fragments, with reaction enthalpies to within 1 kJ mol–1, as well as vibrational terms to within 1.5 cm–1 deviation from experimental values.
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a new global and compact Analytical Representation of the potential energy surface of triatomic systems application to copper nitrosyl and water
Molecular Physics, 2013Co-Authors: Yann Cornaton, Murali B Krishna, Roberto MarquardtAbstract:A new, general Analytical Representation of potential energy surfaces (PES) for triatomic molecules is developed. It is based on a novel, angular-dependent form of the Morse potential extended to two bonds. The very compact Analytical form needs only a few adjustable parameters while yielding a physically sound description of the global behaviour of the interactions in the entire configuration space. As a first example, the global PES of the lowest adiabatic state of water monomer (H2O) is reviewed. Parameters were adjusted to sets of energy points obtained from ab initio calculations at the coupled cluster and multi-reference configuration interaction level of theory. Experimental vibrational band centres of levels below 5000 cm−1 are correctly reproduced to within 3 cm−1; higher lying levels are less well described than in previously determined PES Representations which involved a substantially extended set of adjustable parameters. Spectroscopic and thermodynamic data as well as reaction barriers are o...
Mark S Gordon - One of the best experts on this subject based on the ideXlab platform.
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An Analytical Representation of the lowest potential energy surface for the reaction O(3P)+HCl (X 1Σ+)→OH(X 2Π)+Cl(2P)
Journal of Chemical Physics, 1991Co-Authors: Hiroyasu Koizumi, George C Schatz, Mark S GordonAbstract:We present a new Analytical Representation of the lowest 3A‘ energy surface for the reaction O(3P)+HCl(X 1Σ+)→OH(X 2Π)+Cl(2P). This surface is derived by fitting ab initio calculations, and adjustments are made to the barrier height so that rate constants derived from accurate quantum scattering calculations match the room temperature thermal rate constants. Contributions to thermal and state resolved rate constants arising from reaction on the lowest 3A’ surface are also considered. Comparisons of thermal and state resolved rate constants with experiment are good except at high temperature where the 3A’ contributions are significant.
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an Analytical Representation of the lowest potential energy surface for the reaction o 3p hcl x 1σ oh x 2π cl 2p
Journal of Chemical Physics, 1991Co-Authors: Hiroyasu Koizumi, George C Schatz, Mark S GordonAbstract:We present a new Analytical Representation of the lowest 3A‘ energy surface for the reaction O(3P)+HCl(X 1Σ+)→OH(X 2Π)+Cl(2P). This surface is derived by fitting ab initio calculations, and adjustments are made to the barrier height so that rate constants derived from accurate quantum scattering calculations match the room temperature thermal rate constants. Contributions to thermal and state resolved rate constants arising from reaction on the lowest 3A’ surface are also considered. Comparisons of thermal and state resolved rate constants with experiment are good except at high temperature where the 3A’ contributions are significant.
