Journal ArticleDOI
Calibration-quality adiabatic potential energy surfaces for H-3(+) and its isotopologues
Michele Pavanello,Ludwik Adamowicz,Alexander Alijah,Nikolai F. Zobov,Irina I. Mizus,Oleg L. Polyansky,Jonathan Tennyson,Tamás Szidarovszky,Attila G. Császár +8 more
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TLDR
An extremely accurate global potential energy surface of H(3)(+) resulting from high accuracy ab initio computations and global fit, very accurate nuclear motion calculations of all available experimental line data up to 16,000 cm(-1), and results suggest that the authors can predict accurately the lines of H (3)(+) towards dissociation and thus facilitate their experimental observation.Abstract:
Calibration-quality ab initio adiabatic potential energy surfaces (PES) have been determined for all isotopologues of the molecular ion H3+. The underlying Born–Oppenheimer electronic structure computations used optimized explicitly correlated shifted Gaussian functions. The surfaces include diagonal Born–Oppenheimer corrections computed from the accurate electronic wave functions. A fit to the 41 655 ab initio points is presented which gives a standard deviation better than 0.1 cm−1 when restricted to the points up to 6000 cm−1 above the first dissociation asymptote. Nuclear motion calculations utilizing this PES, called GLH3P, and an exact kinetic energy operator given in orthogonal internal coordinates are presented. The ro-vibrational transition frequencies for H3+, H2D+, and HD 2+ are compared with high resolution measurements. The most sophisticated and complete procedure employed to compute ro-vibrational energy levels, which makes explicit allowance for the inclusion of non-adiabatic effects, reproduces all the known ro-vibrational levels of the H3+ isotopologues considered to better than 0.2 cm−1. This represents a significant (order-of-magnitude) improvement compared to previous studies of transitions in the visible. Careful treatment of linear geometries is important for high frequency transitions and leads to new assignments for some of the previously observed lines. Prospects for further investigations of non-adiabatic effects in the H3+ isotopologues are discussed. In short, the paper presents (a) an extremely accurate global potential energy surface of H3+ resulting from high accuracy ab initio computations and global fit, (b) very accurate nuclear motion calculations of all available experimental line data up to 16 000 cm−1, and (c) results suggest that we can predict accurately the lines of H3+ towards dissociation and thus facilitate their experimental observation.read more
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Theory and application of explicitly correlated Gaussians
Jim Mitroy,Sergiy Bubin,Wataru Horiuchi,Yasuyuki Suzuki,Ludwik Adamowicz,Wojciech Cencek,Krzysztof Szalewicz,Jacek Komasa,D Blume,Kalman Varga +9 more
TL;DR: The variational method complemented with the use of explicitly correlated Gaussian basis functions is one of the most powerful approaches currently used for calculating the properties of few-body systems as mentioned in this paper.
Journal ArticleDOI
New analytical model for the ozone electronic ground state potential surface and accurate ab initio vibrational predictions at high energy range
TL;DR: The major purpose of this work was to provide accurate theoretical predictions for ozone vibrational band centres at the energy range near the dissociation threshold, which would be helpful for understanding the very complicated high-resolution spectra and its analyses currently in progress.
Journal ArticleDOI
First principles intensity calculations of the methane rovibrational spectra in the infrared up to 9300 cm−1
TL;DR: Global calculations of rovibrational spectra and dipole transition intensities of methane using the recent ab initio dipole moment and potential surfaces are reported and positions and line intensities are shown to be in excellent agreement with raw experimental data, even for high energy ranges.
Journal ArticleDOI
Calculation of rotation-vibration energy levels of the water molecule with near-experimental accuracy based on an ab initio potential energy surface.
Oleg L. Polyansky,Oleg L. Polyansky,Roman I. Ovsyannikov,Aleksandra A. Kyuberis,Lorenzo Lodi,Jonathan Tennyson,Nikolai F. Zobov +6 more
TL;DR: It is conjecture that the energy levels of closed-shell molecules with roughly the same number of electrons as water, such as NH3, CH4, and H3O(+), could be calculated to this accuracy using an analogous procedure.
Journal ArticleDOI
Vibration–rotation transition dipoles from first principles
TL;DR: In this article, the first principles calculation of transition dipoles, upon which the intensity is based, relies on three distinct steps: the quantum chemical calculation of the dipole moment surface at a grid of geometries, the accurate representation of this surface using an appropriate functional form and the wave functions used to represent the initial and final states, which in turn depend on the accuracy of the potential energy surface used to generate them.
References
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Book
Molecular Potential Energy Functions
TL;DR: A series of papers describing advances made in recent years in obtaining explicit functions for the potential energy surfaces of small polyatomic molecules can be found in this paper, which emphasizes the general features that potential energy functions should possess rather than the particular functions.
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Diffuse Atomic and Molecular Clouds
TL;DR: In this article, a new systematic classification method for the different types of diffuse clouds: diffuse atomic, diffuse molecular, translucent, and dense is proposed, which can be used as indicators of the physical and chemical conditions within these clouds.
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The diagonal correction to the Born–Oppenheimer approximation: Its effect on the singlet–triplet splitting of CH2 and other molecular effects
TL;DR: In this article, the diagonal correction to the Born-Oppenheimer approximation is predicted by ab initio analytic methods, as has recently been shown by Yarkony and Lengsfield.
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Newton-Type Minimization via the Lanczos Method
TL;DR: In this article, the Lanczos characterization of the linear conjugate-gradient method is used to define a modified Newton method which can be applied to problems that do not necessarily have positive-definite Hessian matrices at all points of the region of interest.