A Monte Carlo error estimator for the expansion of rigid-rotor potential energy surfaces

Rist, Claire; Fauré, Alexandre

doi:10.1007/s10910-011-9821-8

Cited by 36 publications

(29 citation statements)

References 25 publications

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“…At each intermolecular distance, the interaction energy was least-squares fitted, using a 167-term expansion including anisotropies up to l1=10 and l2=4, where the integer indices l1 and l2 refer to the NH3 and H2 angular dependence, respectively. These 167 expansion terms were selected using a Monte Carlo error estimator defined in Rist & Faure (2012). The root mean squared error (RMSE) is lower than 1 cm −1 for R > 5 a0.…”

Section: Potential Energy Surfacementioning

confidence: 99%

Collisional excitation of NH3 by atomic and molecular hydrogen

Bouhafs

Rist

Daniel

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We report extensive theoretical calculations on the rotation-inversion excitation of interstellar ammonia (NH 3 ) due to collisions with atomic and molecular hydrogen (both para-and ortho-H 2 ). Close-coupling calculations are performed for total energies in the range 1-2000 cm −1 and rotational cross sections are obtained for all transitions among the lowest 17 and 34 rotation-inversion levels of ortho-and para-NH 3 , respectively. Rate coefficients are deduced for kinetic temperatures up to 200 K. Propensity rules for the three colliding partners are discussed and we also compare the new results to previous calculations for the spherically symmetrical He and para-H 2 projectiles. Significant differences are found between the different sets of calculations. Finally, we test the impact of the new rate coefficients on the calibration of the ammonia thermometer. We find that the calibration curve is only weakly sensitive to the colliding partner and we confirm that the ammonia thermometer is robust.

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Section: Potential Energy Surfacementioning

confidence: 99%

Collisional excitation of NH3 by atomic and molecular hydrogen

Bouhafs

Rist

Daniel

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…that they allow an estimate of the accuracy of each expansion coefficients, 29 as illustrated below.…”

Section: Fig 4 Nh 3 -Co Interaction Energies For Different Basis Sementioning

confidence: 99%

Rotational study of the NH3–CO complex: Millimeter-wave measurements and ab initio calculations

Surin

Потапов

Dolgov

et al. 2015

The Journal of Chemical Physics

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The rotational spectrum of the van der Waals complex NH 3 -CO has been measured with the intracavity OROTRON jet spectrometer in the frequency range of 112-139 GHz. Newly observed and assigned transitions belong to the K = 0-0, K = 1-1, K = 1-0, and K = 2-1 subbands correlating with the rotationless ( j k ) NH3 = 0 0 ground state of free ortho-NH 3 and the K = 0-1 and K = 2-1 subbands correlating with the ( j k ) NH3 = 1 1 ground state of free para-NH 3 . The (approximate) quantum number K is the projection of the total angular momentum J on the intermolecular axis. Some of these transitions are continuations to higher J values of transition series observed previously [C. Xia et al., Mol. Phys. 99, 643 (2001)], the other transitions constitute newly detected subbands. The new data were analyzed together with the known millimeter-wave and microwave transitions in order to determine the molecular parameters of the ortho-NH 3 -CO and para-NH 3 -CO complexes. Accompanying ab initio calculations of the intermolecular potential energy surface (PES) of NH 3 -CO has been carried out at the explicitly correlated coupled cluster level of theory with single, double, and perturbative triple excitations and an augmented correlation-consistent triple zeta basis set. The global minimum of the five-dimensional PES corresponds to an approximately T-shaped structure with the N atom closest to the CO subunit and binding energy D e = 359.21 cm −1 . The bound rovibrational levels of the NH 3 -CO complex were calculated for total angular momentum J = 0-6 on this intermolecular potential surface and compared with the experimental results. The calculated dissociation energies D 0 are 210.43 and 218.66 cm −1 for ortho-NH 3 -CO and para-NH 3 -CO, respectively. C 2015 AIP Publishing LLC. [http://dx

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“…This choice of grid provides a uniform sampling of the differential solid angle sin θ 1 dθ 1 sin θ 2 dθ 2 dφ 2 . 40 The OH-H 2 distance was spanned by 32 values of R ranging from 3.5 a 0 to 16 a 0 .…”

Section: A Mrci Calculationsmentioning

confidence: 99%

The interaction of OH(X2Π) with H2: Ab initio potential energy surfaces and bound states

Kłos

Alexander

Avoird

et al. 2014

The Journal of Chemical Physics

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For the interaction of OH(X 2 ) with H 2 , under the assumption of fixed OH and H 2 bond distances, we have determined two new sets of four-dimensional ab initio potential energy surfaces (PES's). The first set of PES's was computed with the multi-reference configuration interaction method [MRCISD+Q(Davidson)], and the second set with an explicitly correlated coupled cluster method [RCCSD(T)-F12a] sampling the subset of geometries possessing a plane of symmetry. Both sets of PES's are fit to an analytical form suitable for bound state and scattering calculations. The CCSD(T) dissociation energies (D 0 ) of the OH-para-H 2 and the OH-ortho-H 2 complexes are computed to be 36.1 and 53.7 cm −1 . The latter value is in excellent agreement with the experimental value of 54 cm −1 .

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A Monte Carlo error estimator for the expansion of rigid-rotor potential energy surfaces

Cited by 36 publications

References 25 publications

Collisional excitation of NH3 by atomic and molecular hydrogen

Collisional excitation of NH3 by atomic and molecular hydrogen

Rotational study of the NH3–CO complex: Millimeter-wave measurements and ab initio calculations

The interaction of OH(X2Π) with H2: Ab initio potential energy surfaces and bound states

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