Using <i>ScalIT</i> for Performing Accurate Rovibrational Spectroscopy Calculations for Triatomic Molecules: A Practical Guide

Abstract

This paper presents a practical guide for use of the ScalIT software package to perform highly accurate bound rovibrational spectroscopy calculations for triatomic molecules. At its core, ScalIT serves as a massively scalable iterative sparse matrix solver, while assisting modules serve to create rovibrational Hamiltonian matrices, and analyze computed energy levels (eigenvalues) and wavefunctions (eigenvectors). Some of the methods incorporated into the package include: phase space optimized discrete variable representation, preconditioned inexact spectral transform, and optimal separable basis preconditioning. ScalIT has previously been implemented successfully for a wide range of chemical applications, allowing even the most state-of-the-art calculations to be computed with relative ease, across a large number of computational cores, in a short amount of time.

Double Proton Transfer in the Dimer of Formic Acid: An Efficient Quantum Mechanical Scheme

“…However, loosening it too much will highly increase the number of steps for Lanczos iteration, which is much slower than QMR iteration. The PIST method has also been employed in other applications (Bian and Poirier, 2004; Li and Bian, 2008; Brandon and Poirier, 2014; Petty and Poirier, 2014).…”

Theoretical methods for the rotation–vibration spectra of triatomic molecules: distributed Gaussian functions compared with hyperspherical coordinates

“…However the approximation can fail for certain molecular systems. HO 2 , for example, is one of those cases in which the comparison [37][38][39] between some of these decoupling schemes and calculations performed with methods such as the ScallT program developed by Poirier and collaborators [40,41] or the Chebyshev filter diagonalization method employed by Zhang and Smith [42][43][44][45] reveals the necessity of a proper account for the Coriolis coupling terms.…”

“…Ω, and the index v Γ of the corresponding vibrational state in each irreducible representation (see Eqs. (41)(42)(43)) are given in the first, third and fourth columns, respectively. The rovibrational Γ Ω vib (fifth column), rotational Γ rot (sixth column) and total Γ (seventh column) symmetries are also indicated.…”

Exact Numerical Methods for Stationary-State-Based Quantum Dynamics of Complex Polyatomic Molecules

“…Several codes have been developed which can perform these numerically very demanding quantum-chemical computations: ElVibRot Nauts, 2002, Lauvergnat, 2019), GENIUSH , Fábri et al, 2011a, MCTDH (Meyer et al, 2009), NITROGEN (Changala, 2019), TROVE (Yurchenko et al, 2007), codes due to Carrington (Manzhos et al, 2009, Manzhos and Carrington, Jr., 2016, Poirier (Poirier, 2003b, Chen and Poirier, 2006, Petty and Poirier, 2014, Yu (Yu, 2002(Yu, , 2004a(Yu, ,b, 2006, and perhaps there are others, as well. Note that for triatomic systems, for which a completely general internal-coordinate Hamiltonian, often referred to as the Sutclie-Tennyson Hamiltonian (Sutclie and Tennyson, 1991), could be developed, there are lot more codes available which are similar in spirit to those mentioned above, e.g., DVR3D , ScalIT (Petty and Poirier, 2014), D 2 FOPI , and codes due to Guo (Ma et al, 1999) and Schwenke (Schwenke, 1992, Klepeis et al, 1993. For four-atomic molecules it is not possible to develop a Hamiltonian which would cover all possible internal coordinate systems.…”