Car-Parrinello molecular dynamics CPMD

Figure 3. Proton conduction mechanism in iiquid imida-zoie, as revealed by a Car—Parrinello molecular dynamics (CPMD) simulation.3 Note the similarities with the proton conduction mechanism in water (see Figure 1).

The first way has been followed in what has become known as Car-Parrinello molecular dynamics (CPMD) (9). A solute and 60-90 solvent molecules are considered to represent the system, and the QM calculations are performed with density functionals, usually of generalised gradient approximation type (GGA), such as the Becke-Lee-Young-Parr (BLYP) (10) or the Perdew-Burke-Enzerhofer (PBE) (11,12) functionals. It is clear that the semiempirical character of concurrent density functional theory (DFT) methods and the use of these simple functionals imply a number of error sources and do not really provide a method-inherent control procedure to test the reliability of results. Recently it has been shown that these functionals even do not enable a correct description of the solvent water itself, as at ambient temperature they will describe water not as liquid but as supercooled system... 

Architecture of Hydrates and Local Structure of Acetic Acid Aqueous Solution Ab Initio Calculations and Car-Parrinello Molecular Dynamics (CPMD) Simulations on Hydrogen-Bonding Rings, Network, and Intra-Hydrate Protonation in Multi-Hydrates of Acetic Acid Monomer... 

Both the experimental and theoretical studies indicate that the interactions between acetic acid and water molecules are more competitive in dilute aqueous solution. However to our knowledge, the specific interactions between acetic acid and water molecules are still not well understood, especially in such as the nature of hydrogen bonding, the bonds networking, the rule in architecture of larger hydration compounds, deprotonation of acetic acid in solution, stability of the hydrated proton, the local structure of its aqueous solution, and so on. In the present work, we have performed ab initio calculations on multi-hydrates (rich water hydration compounds) of acetic acid, and ab initio Car-Parrinello molecular dynamics (CPMD) [20] simulations on acetic acid monomer and water system (at dilute aqueous solution condition) to find something helpful for interpreting the nature of acetic acid aqueous solution. 

At present three different codes are widely used for calculations of the structural and spectroscopic properties of H-bonded crystals, for example see Refs. [82-85]. The Car-Parrinello molecular dynamics (CPMD) program [86] and the Vienna ab initio simulation program (VASP) [87, 88] use a plane wave basis set, while an atom centered set is used with periodic boundary conditions in the CRYSTAL... 

Recent advances in first-principles molecular dynamics (MD) calculations, which follow the Newtonian dynamics of classically treated nuclei, have made electronic-structure calculations applicable to the study of large systems where previously only classical simulations were possible. Examples of quantum-mechanical (QM) simulation methods are Born-Oppenheimer molecular dynamics (BOMD), Car-Parrinello molecular dynamics (CPMD), tight-binding molecular dynamics (TBMD), atom-centered density matrix propagation molecular dynamics (ADMPMD), and wavepacket ab idtb molecular dynamics (WPAIMD). 

Therefore, we decided to perform Car-Parrinello Molecular Dynamics (CPMD) on derivative IV and compared the quantum-chemistry results with the corresponding conventional molecular dynamics. Sampling of the puckering angle P during the study yielded the ID-free energy profiles reported in Fig. 7. The probability distribution is represented as a function of the coordinate P obtained from MD data, combining all values of 9m (see computational details). In these experiments, P and 0m are no... 

Figure 13 Snapshot of li solvation in EC solvent obtained by Car-Parrinello molecular dynamics (CPMD) simulation at 350.0K. LP and the three strongly coordinated EC molecules are highlighted.

Another approach to the calculation of IR spectra of hydrogen-bonded complexes is based on linear response theory, in which the spectral density is the Fourier transform of the autocorrelation function of the dipole moment operator involved in the IR transition [62,63]. Recently Car-Parrinello molecular dynamics (CPMD) [73] has been used to simulate IR spectra of hydrogen-bonded systems [64-72]. 

The reconstruction of the bandshape of the imidazole crystal was also performed using Car-Parrinello molecular dynamics (CPMD) simulation [73] of the unit cell of the crystal the results reproduce both the frequencies and intensities of the experimental IR spectrum of bands reasonably well, which we attribute to the application of dipole moment dynamics. The results are presented in Fig. 8 [70]. These and other recent CPMD calculations, on 2-hydroxy-5-nitrobenzamide crystal [71], oxalic acid dihydrate [72], and other systems [64-69], show that the CPMD method is adequate for spectroscopic investigations of complex systems with hydrogen bonds since it takes into account most of mechanisms determining the hydrogen bond dynamics (anharmonicity, couplings between vibrational modes, and intermolecular interactions in crystals). 

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