Browsing by Author "3cdfbe39ac1842deaf2a5e186ec1ed9c"
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Ab Initio Study of the CO–N2 Complex: a New Highly Accurate Intermolecular Potential Energy Surface and Rovibrational Spectrum
Cybulski, Hubert; Henriksen, Christian; Dawes, Richard; Wang, XiaoGang; Bora, Neha; Avila, Gustavo; Carrington, Tucker Jr; Fernández, Berta (20180301)A new, highly accurate ab initio groundstate intermolecular potentialenergy surface (IPES) for the CON2 complex is presented. Thousands of interaction energies calculated with the CCSD(T) method and Dunning’s augccpVQZ ... 
A Comparison of Methods for Determining the Time Step When Propagating with the Lanczos Algorithm
Mohankumar, N.; Carrington, Tucker Jr (2019)To use the short iterative Lanczos algorithm to solve the timedependent Schroedinger equation, one must choose, for a given Lanczos space size, a timestep. We compare the derivation of the wellknown Lubich and Hochbruck ... 
Computational Study of the RoVibrational Spectrum of CO–CO2
CastroJuárez, Eduardo; Wang, XiaoGang; Carrington, Tucker Jr; QuintasSánchez, Ernesto; Dawes, Richard (2019)An accurate ab initio groundstate intermolecular potential energy surface (PES) was determined for the CO–CO2 van der Waals dimer. The Lanczos algorithm was used to compute rovibrational energies on this PES. For both the ... 
Computational Study of the Rovibrational Spectra of CH2D+ and CHD2+
Simmons, Jesse; Wang, XiaoGang; Carrington, Tucker Jr (2019)In this paper, we present rovibrational energy levels of CH2D+ and CHD2+. They are computed with a large basis and the Lanczos algorithm. CH2D+ and CHD2+ are believed to play an important role in interstellar space, but ... 
Computing Vibrational Energy Levels of CH4 With a Smolyak Collocation Method
Avila, Gustavo; Carrington, Tucker Jr (20171230)In this paper, we demonstrate that it is possible to apply collocation to compute vibrational energy levels of a fiveatom molecule using an exact kinetic energy operator (with cross terms and coordinatedependent ... 
Computing Vibration–RotationTunnelling Levels of HOD Dimer
Wang, XiaoGang; Carrington, Tucker Jr (2017)Using an accurate 6D water dimer potential energy surface, we compute vibrationrotation tunnelling levels of HOD dimer, by assuming that the two monomers are rigid. HOD dimer has two isomers, a Dbonded isomer and an ... 
FullDimensional Calculations of Rovibrational Levels of FiveAtom Molecules Using Two Different Strategies: Applications to CH4, CHD3, CH3D and CH3F
Zhao, Zhiqiang; Chen, Jun; Zhang, Zhaojun; Zhang, Dong H.; Wang, XiaoGang; Carrington, Tucker Jr; Gatti, Fabien (2018)Quantum mechanical calculations of rovibrational energies of CH4, CHD3, CH3D, and CH3F were made with two different numerical approaches. Both use polyspherical coordinates. The computed energy levels agree, conﬁrming the ... 
The He2  OCS Complex: Comparison Between Theory and Experiment
Oliaee, J. Norooz; MoazzenAhmadi, N.; McKellar, A.R.W.; Wang, XiaoGang; Carrington, Tucker Jr (20171031)OCS is an ideal probe for quantum solvation effects in cold helium clusters. He2OCS is the “second step” in going from a single OCS molecule to a large doped superfluid helium cluster. Here assignment of the spectrum of ... 
Iterative Methods for Computing Vibrational Spectra
Carrington, Tucker Jr (20171221)I review some computational methods for calculating vibrational spectra. They all use iterative eigensolvers to compute eigenvalues of a Hamiltonian matrix by evaluating matrixvector products. A directproduct basis can ... 
Machine learning optimization of the collocation point set for solving the electronic Schrödinger equation
Ku, Jonas; Kamath, Aditya; Carrington, Tucker Jr; Manzhos, Sergei (2019)The rectangular collocation approach makes it possible to solve the Schrödinger equation with basis functions that do not have amplitude in all regions in which wavefunctions have significant amplitude. Collocation points ... 
A MultiDimensional Smolyak Collocation Method in Curvilinear Coordinates for Computing Vibrational Spectra
Avila, Gustavo; Carrington, Tucker Jr (20151202)In this paper, we improve the collocation method for computing vibrational spectra that was presented in Avila and Carrington, Jr. [J. Chem. Phys. 139, 134114 (2013)]. Using an iterative eigensolver, energy levels and ... 
Neural Networks vs Gaussian Process Regression for Representing Potential Energy Surfaces: a Comparative Study of Fit Quality and Vibrational Spectrum Accuracy
Kamath, Aditya; VargasHernández, Rodrigo A.; Krems, Roman V.; Carrington, Tucker Jr; Manzhos, Sergei (2018)For molecules with more than three atoms, it is difficult to fit or interpolate a potential energy surface (PES) from a small number of (usually ab initio) energies at points. Many methods have been proposed in recent ... 
A New CollocationBased MultiConﬁguration TimeDependent Hartree (MCTDH) Approach for Solving the Schrödinger Equation With a General Potential Energy Surface
Wodraszka, Robert; Carrington, Tucker Jr (20180108)We present a new collocationbased multiconﬁguration timedependent Hartree (MCTDH) approach for solving the Schrödinger equation required to compute (ro)vibrational spectra, photodissociation cross sections, reaction ... 
A Pruned CollocationBased Multiconfiguration TimeDependent Hartree Approach Using a Smolyak Grid for Solving the Schrödinger Equation with a General Potential Energy Surface
Wodraszka, Robert; Carrington, Tucker Jr (2019)Standard multiconfiguration timedependent Hartree (MCTDH) calculations use a direct product basis and rely on the potential being a sum of products (SOPs). The size of the direct product MCTDH basis scales exponentially ... 
Redundant Coordinates in Quantum Mechanics
Toombs, Eric; Carrington, Tucker Jr (2018)We present a kinetic energy operator and inner product that can be used to solve the Schroedinger equation in redundant coordinates. The goal is to develop equations and a computational procedure that can be used with N ... 
Using an Iterative Eigensolver and Intertwined Rank Reduction to Compute Vibrational Spectra of Molecules With More Than a Dozen Atoms: Uracil and Naphthalene
Thomas, Phillip S.; Carrington, Tucker Jr; Agarwal, Jay; Schaefer, Henry F. III (20170210)We use a direct product basis, basis vectors computed by evaluating matrixvector products, and rank reduction to calculate vibrational energy levels of uracil and naphthalene, with 12 and 18 atoms, respectively. A matrix ... 
Using Collocation and a Hierarchical Basis to Solve the Vibrational Schrödinger Equation
Zak, Emil J.; Carrington, Tucker Jr (2019)We show that it is possible to compute vibrational energy levels of polyatomic molecules with a collocation method and a basis of products of onedimensional harmonic oscillator functions pruned so that it does not include ... 
Using Monomer Vibrational Wavefunctions to Compute Numerically Exact (12D) Rovibrational Levels of Water Dimer
Wang, XiaoGang; Carrington, Tucker Jr (2017)We compute numerically exact rovibrational levels of water dimer, with 12 vibrational coordinates, on the accurate CCpol8sf ab initio ﬂexible monomer potential energy surface[J. Chem. Phys. 137, 014305 (2012)]. It does ... 
Using MultiDimensional Smolyak Interpolation to Make a SumofProductsPotential
Avila, Gustavo; Carrington, Tucker Jr (20150727)We propose a new method for obtaining potential energy surfaces in sumofproducts (SOP) form. If the number of terms is small enough, a SOP potential surface significantly reduces the cost of quantum dynamics calculations ... 
Using Quadrature and an Iterative Eigensolver to Compute FineStructure RoVibrational Levels of Van der Waals Complexes: NH(Σ−3)–He, O2(Σg−3)–Ar, and O2(Σg−3)–He
Wang, XiaoGang; Carrington, Tucker Jr (2019)We introduce a new method for computing spectra of molecules for which a spinspin term in the Hamiltonian has an important effect. In previous calculations, matrix elements of the spinspin term and of the potential were ...