12 research outputs found
Ab initio molecular dynamics study for C–Br dissociation within BrH2C–C≡C(ads) adsorbed on an Ag(111) surface: a short-time Fourier transform approach
[[abstract]]The reaction dynamics for C–Br dissociation within BrH2C–C≡CH(ads) adsorbed on an Ag(111) surface has been investigated by combining density functional theory-based molecular dynamics simulations with short-time Fourier transform (STFT) analysis of the dipole moment autocorrelation function. Two possible reaction pathways for C–Br scission within BrH2C–C≡CH(ads) have been proposed on the basis of different initial structural models. Firstly, the initial perpendicular orientation of adsorbed BrH2C–C≡CH(ads) with a stronger C–Br bond will undergo dynamic rotation leading to the final parallel orientation of BrH2C–C≡CH(ads) to cause the C–Br scission, namely, an indirect dissociation pathway. Secondly, the initial parallel orientation of adsorbed BrH2C–C≡C(ads) with a weaker C–Br bond will directly cause the C–Br scission within BrH2C–C≡CH(ads), namely, a direct dissociation pathway. To further investigate the evolution of different vibrational modes of BrH2C–C≡CH(ads) along these two reaction pathways, the STFT analysis is performed to illustrate that the infrared (IR) active peaks of BrH2C–C≡CH(ads) such as vCH2 [2956 cm−1(s) and 3020 cm−1(as)], v≡CH (3320 cm−1) and vC≡C (2150 cm−1) gradually vanish as the rupture of C–Br bond occurs and then the resulting IR active peaks such as C=C=C (1812 cm−1), ω-CH2 (780 cm−1) and δ-CH (894 cm−1) appear due to the formation of H2C=C=CH(ads) which are in a good agreement with experimental reflection adsorption infrared spectrum (RAIRS) at temperatures of 110 and 200 K, respectively. Finally, the total energy profiles indicate that the reaction barriers for the scission of C–Br within BrH2C–C≡CH(ads) along both direct and indirect dissociation pathways are very close due to a similar rupture of C–Br bond leading to a similar transition state.[[sponsorship]]MOST[[notice]]補æ£å®Œ
Water radiolysis by low-energy carbon projectiles from first-principles molecular dynamics
Thermo-dynamical contours of electronic-vibrational spectra simulated using the statistical quantum-mechanical methods
Hydrogen bonds in quinoline N-oxide derivatives: first-principle molecular dynamics and metadynamics ground state study
Hydrogen bond dynamics and vibrational spectral diffusion in aqueous solution of acetone: A first principles molecular dynamics study#
Excited states behavior of nucleobases in solution: insights from computational studies
We review the most significant results obtained in the study of isolated nucleobases in solution by quantum mechanical methods, trying to highlight also the most relevant open issues. We concisely discuss some methodological issues relevant to the study of molecular electronic excited molecular states in condensed phases, focussing on the methods most commonly applied to the study of nucleobases, i.e. continuum models as the Polarizable Continuum Model and explicit solvation models. We analyse how the solvent changes the relative energy of the lowest energy excited states in the Franck-Condon region, their minima and the Conical Intersections among the different states, interpreting the experimental optical spectra, both steady state and time-resolved. Several methods are available for accurately including solvent effects in the Franck-Condon region, and for most of the nucleobases the solvent shift on the different excited states can be considered assessed. The study of the excited state decay, both radiative and non-radiative, in solution still poses instead significant theoretical challenges
Real-World Predictions from Ab Initio Molecular Dynamics Simulations
In this review we present the techniques of ab initio molecular dynamics simulation improved to its current stage where the analysis of existing processes and the prediction of further chemical features and real-world processes are feasible. For this reason we describe the relevant developments in ab initio molecular dynamics leading to this stage. Among them, parallel implementations, different basis set functions, density functionals, and van der Waals corrections are reported. The chemical features accessible through AIMD are discussed. These are IR, NMR, as well as EXAFS spectra, sampling methods like metadynamics and others, Wannier functions, dipole moments of molecules in condensed phase, and many other properties. Electrochemical reactions investigated by ab initio molecular dynamics methods in solution, on surfaces as well as complex interfaces, are also presented
TDDFT and quantum-classical dynamics: A universal tool describing the dynamics of matter
Time-dependent density functional theory (TDDFT) is currently the most efficient approach allowing to describe electronic dynamics in complex systems, from isolated molecules to the condensed phase. TDDFT has been employed to investigate an extremely wide range of time-dependent phenomena, as spin dynamics in solids, charge and energy transport in nanoscale devices, and photoinduced exciton transfer in molecular aggregates. It is therefore nearly impossible to give a general account of all developments and applications of TDDFT in material science, as well as in physics and chemistry. A large variety of aspects are covered throughout these volumes. In the present chapter, we will limit our presentation to the description of TDDFT developments and applications in the field of quantum molecular dynamics simulations in combination with trajectory-based approaches for the study of nonadiabatic excited-state phenomena. We will present different quantum-classical strategies used to describe the coupled dynamics of electrons and nuclei underlying nonadiabatic processes. In addition, we will give an account of the most recent applications with the aim of illustrating the nature of the problems that can be addressed with the help of these approaches. The potential, as well as the limitations, of the presented methods is discussed, along with possible avenues for future developments in TDDFT and nonadiabatic dynamics