Standard molecular and driven dynamics are used to analyze prominent spectral features in the H5O2+ infrared spectrum. In method, Hamiltonian is augmented with a time-dependent term, μ · ε0 sin(ωt), where dipole moment of H5O2+, electric field, ω frequency. The magnitude field determines whether driving mild (the harmonic limit) or strong (anharmonic motion mode coupling). We spectrum wavenumber range from 600 1900 cm-1, recent experimental measurements available for H5O2+. On basis...

There has been renewed interest in carbon nanoscale structures. Experimental measurements at 4.7 K and subsequent first-principles-based vibrational diffusion Monte Carlo simulations 0 recently showed that the aromatic cyclo[10]carbon prefers a D5h pentagon-like structure to regular D10h decagon. This symmetry breaking is due second-order Jahn–Teller effect (JTE) amply described literature for cumulenic cyclo[4m + 2]carbon clusters. Yet temperature dependence of JTE clusters general...

We report experimental vibrational action spectra (210–2200 cm–1) and calculated IR spectra, using recent ab initio potential energy dipole moment surfaces, of H7O3+ H9O4+. focus on prominent far-IR bands, which postharmonic analyses show, arise from two types intermolecular motions, i.e., hydrogen bond stretching terminal water wagging modes, that are similar in both clusters. The good agreement between experiment theory further validates the accuracy was used a theoretical study concluded...

In this work, we present infrared spectra of H(5)O(2)(+) and its D(5)O(2)(+), D(4)HO(2)(+), DH(4)O(2)(+) isotopologues calculated by classical molecular dynamics simulations on an accurate potential energy surface generated from CCSD(T) calculations, as well the BLYP DFT sampled means Car-Parrinello algorithm. The obtained with internal energies corresponding to a temperature about 30 K are in overall good agreement those experimental measurements quantum dynamical simulations.

New experimental measurements [Sun et al., Nature 2023, 623, 972] of the cyclic C10 reveal a cumulenic pentagon-like D5h structure at ∼5 K. However, long-standing presumption that large zero-point vibrational energy combined with an extremely flat ↔ D10h isomerization pathway washes out pentagonal and yields symmetric decagon remains odds experiment. We resolve this issue our fitting approach based on bond-order charge-density matrix expressed in permutationally invariant polynomials. train...

In this work, we present infrared (IR) spectra of H7O3(+) and its deuterium isotopomers calculated by direct molecular dynamics (MD) simulations at the B3LYP/6-31+G** computational level. The obtained 100, 300, 500 K were compared to available experimental observations, spectral features assigned using normal-mode analysis (NMA) driven (DMD). Spectral peaks 2410 2540 cm(-1) asymmetric symmetric stretches bridging hydrogen (BH) NMA. weak 2166 2275 a combination band BH stretch, H2O in phase...

The driven molecular-dynamics (DMD) method, recently proposed by Bowman, Zhang, and Brown [J. Chem. Phys. 119, 646 (2003)], has been implemented into the TINKER molecular modeling program package. DMD method yields frequencies normal modes without evaluation of Hessian matrix. It employs an external harmonic driving term that can be used to scan spectrum determine resonant absorptions. motions, induced at frequencies, correspond normal-mode vibrations. In current work we apply a 20-residue...

We present the infrared spectra of H3O2(-) and D3O2(-) calculated using MP2 direct molecular dynamics approach at temperatures 100 300 K. The spectral peaks were assigned normal-mode analysis, instantaneous isotopic substitution, polarized absorptions, analysis position-position correlation function. Our results predict bridging hydrogen stretch between 600 900 cm(-1) bend vibrations 1250 1650 cm(-1). also examine two DFT methods (B3PW91 B3LYP) report on differences them spectra.

The electronic energy in the Hartree-Fock (HF) theory is trace of product charge density matrix (CDM) with one-electron and two-electron matrices represented an atomic orbital basis, where also a function same CDM. In this work, we examine formalism analytic representation generic molecular potential surface (PES) as sum linearly parameterized HF correction term, latter formally representing electron correlation energy, parameterized, by expressing elements CDM using permutationally...

A representation for learning potential energy surfaces (PESs) in terms of permutationally invariant polynomials (PIPs) using the Hartree-Fock expression electronic is proposed. Our approach based on one-electron core Hamiltonian weighted by configuration-dependent elements bond-order charge density matrix (CDM). While previously reported model used an

We report IR spectra of H5O2(+) and H5O2(+)·Ar their deuterium isotopologues using ab initio molecular dynamics. The trajectories were propagated as microcanonical (NVE) ensembles at energies corresponding to temperatures 50 100 K. potential energy surface is calculated on-the-fly the MP2/aug-cc-pVDZ level theory. calculations show that adding an argon atom introduces symmetry breaking in Zundel core ion, causes blueshift shared proton vibration by about 200 cm(-1), leads splitting OH...

Conventional normal-mode analysis of molecular vibrations requires computation and storage the Hessian matrix. For a typical biological system such can reach several gigabytes posing difficulties for straightforward implementation. In this work we discuss an iterative block method to carry out full diagonalization while only storing few vectors in memory. The approach is based on conjugate gradient formulation Davidson algorithm simultaneous optimization L roots, where our case 10 < 300....

We investigate the utility of driven molecular dynamics (DMD) approach to complex vibrations by applying it linear clusters with several degenerate vibrational modes and infrared (IR) intense combination bands. Here, prominent features in N4H+ N4D+ IR spectra, reported described others previously, have been characterized for first time DMD using recently published high-level potential dipole moment surfaces. Namely, calculations closely correlate parallel proton stretch vibration N4H+, at...

We describe an approach to constructing analytic Cartesian representation of the molecular dipole polarizability tensor surface in terms polynomials interatomic distances with a training set ab initio data points obtained from dynamics (MD) simulation or by any other available means. The proposed formulation is based on perturbation treatment unmodified point model Applequist [ J. Am. Chem. Soc. 1972, 94, 2952] and shown here be, construction (i) free short-range singularities...

We report first-principles molecular dynamics (MD) and dipole-driven (μ-DMD) simulations of the hydrogen oxalate anion at MP2/aug-cc-pVDZ level theory. examine role vibrational coupling between OH stretching bands, that is, fundamental a few combination bands spanning 2900-3100 cm-1 range, several low-frequency bending modes. The modes 300 825 play crucial in proton-transfer motion. Strong involvement CO2 CCO CC vibrations indicate these large amplitude motions cause shortening O···O...

A linearly parameterized functional form for a Cartesian representation of molecular dipole polarizability tensor surfaces (PTS) is described. The proposed expression the PTS linearization recently reported power series ansatz original Applequist model, which by construction non-linear in parameter space. This new approach possesses (i) unique solution to least-squares fitting problem; (ii) low level computational complexity resulting linear regression procedure, comparable those potential...

In this work, we describe ab initio calculations and assignment of infrared (IR) spectra hydrogen-bonded ion-molecular complexes that involve a fluxional proton: the linear N2H+···OC N2D+···OC complexes. Given challenges describing proton dynamics especially its IR activity, use electric field-driven classical trajectories, i.e., driven molecular (DMD) method was developed by us in recent years for similar applications, conjunction with high-level electronic structure theory. Namely, present...

Dominick Pierre-Jacquesa, Ciara Tylera, Jason Dykea, Alexey L. Kaledinb & Martina Kaledina* a Department of Chemistry Biochemistry, Kennesaw State University, Kennesaw, GA, USAb Cherry Emerson Center for Scientific Computation, Emory Atlanta, USA

Abstract The exact expressions for the dipole, quadrupole, and octupoles of a collection N point charges involve summations corresponding tensors over sites weighted by their charge magnitudes. When are atoms (in molecule) ‐site formula is an approximation, one must integrate electron density to recover multipoles. In present work we revisit ( + 1)/2‐site model Hall (Chem. Phys. Lett. 6 , 501, 1973) purpose fitting ab initio derived multipole moment hypersurfaces using permutationally...

We present molecular dynamics (MD), polarizability driven MD (α-DMD), and pump-probe simulations of Raman spectra the protonated nitrogen dimer N4H+, some its isotopologues, using explicitly correlated coupled-cluster singles doubles with perturbative triples [CCSD(T)]-F12b/aug-cc-pVTZ based potential energy surface in permutationally invariant polynomials (PIPs) Yu et al. [J. Phys. Chem. A 119, 11623 (2015)] a corresponding PIP-derived CCSD(T)/aug-cc-pVTZ-tr (N:spd, H:sp) tensor (PTS),...