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Physicochemical Properties of Nanomaterials from in silico Simulations: An Introduction to Density Functional Theory and Beyond
Published in Agnieszka Gajewicz, Tomasz Puzyn, Computational Nanotoxicology, 2019
Laura Escorihuela, Alberto Fernández, Robert Rallo, Benjamí Martorell
The implicit solvent models have helped to study chemical reactions and materials in solution. However, some difficulties exist with the methods. In the case of the COSMO, in an ideal conductor the potential in the surfaces of the cavity should cease, but in real solvents with low permittivity, this can create instabilities in the cavity surface, making difficult the convergence of the calculations. Besides, the fact that we include corrections in the electronic structure makes the DFT calculation more expensive in computational terms. And, of course, the final results will depend on the XC functional used for the simulation.
Li -Ion Battery Materials and Electrolytes
Published in Aneeya Kumar Samantara, Satyajit Ratha, Electrochemical Energy Conversion and Storage Systems for Future Sustainability, 2020
In the quantum chemical simulations, the electrolytic solvents are represented by the two solvation models; implicit solvent model and explicit solvent model (Bryantsev, 2012; Marenich et al., 2009; Rayne et al., 2010). The basis of the implicit continuum model is the sharp boundary between the solute and the bulk of the solvent, represented as a structure-less polarizable medium, characterized by its dielectric constant (Tomasi et al., 2005). In these models, the molecule/cluster under investigation is located inside a cavity surrounded by a homogeneous dielectric medium of the solvents such as; acetonitrile (MeCN, ε = 35.6), EC (ε = 89.6), propylene carbonate (PC, ε = 64.0), Diethylene carbonate (DEC, ε = 2.40), DMC (ε = 7.15) and Triethylene glycol dimethyl ether (Triglime, ε = 7.94). The implicit solvent model has been successfully applied in the investigation of the chemical reaction within the surrounding medium (Kushwaha et al., 2017, 2018; Kushwaha and Nayak, 2017), There are several continuum models has proposed for expressing the solvent media, out of which polarizable continuum model (PCM) is generally used to represent continuum dielectric medium. Mathematically, the PCM is expressed by the Poisson-Boltzmann equation which is an expansion term of Poisson’s equation. Recently solvation model on density (SMD) is getting much attention for solvation model (Marenich et al., 2009). Similar to the PCM, the SMD model solve the Poisson-Boltzmann equation analytically, only difference is that SMD model used specific parameterize radii for the construction of cavity. The conductor boundary condition based COSMO solvation model is also an implicit solvent model (Klamt and Schüürmann, 1993). The computational cost calculation using the implicit model is lower in comparison to others while is does not maintain the high accuracy especially reaction mechanism. In the explicit solvation model, the molecular solvents form the solvation shell (changes during transfer between the electrodes) around the Li+ ion, either in the electrolyte or at the electrode interfaces. For example, in the case of EC, the coordination number of Li+ has been found to be four, which reduces at the interfaces (Bhatt et al., 2012; Bhatt and O’Dwyer, 2014; Cui et al., 2016). The explicit solvent model provides the more realistic picture of the solute-solvent interaction in comparison to implicit solvent model. Although the computational cost is the major drawback of the explicit solvent model.
3DRISM-HI-D2MSA: an improved analytic theory to compute solvent structure around hydrophobic solutes with proper treatment of solute–solvent electrostatic interactions
Published in Molecular Physics, 2018
Siqin Cao, Lizhe Zhu, Xuhui Huang
Solvents play important roles in many chemical and biological processes, providing a different environment from the vacuum. Among the theoretical approaches that incorporate the solvation effect, the most widely used methods are the explicit solvent molecular dynamic (MD) simulation [1], the continuum solvent models [2–6] and the integration equation theory (IET) [7–51]. The MD simulations can provide the most accurate and detailed information of solvation effects, but require significant computational cost to sample both the solute conformations and solvent distributions. The continuum solvent model is highly efficient in calculating certain solvent properties around a given structure of solutes, but cannot address details of the solvation structure or organic solvents of arbitrary types. As a method in between, the IET can provide solvation details of both water and organic solvents while being more efficient than the explicit solvent simulations [7].
On the influence of dimerisation of lumiflavin in aqueous solution on its optical spectra – a quantum chemical study
Published in Molecular Physics, 2019
Daria Brisker-Klaiman, Andreas Dreuw
The spectroscopic features of lumiflavin (L) in water have been studied. To model the aqueous environment several solvent models were used starting from gas-phase calculations, explicit solvation, continuum solvation model and QM/MM/MD approach. Another aspect of aqueous solvation on lumiflavin in water is its dimerisation, which is known to occur both in aqueous solution [19] and in biological environments [20]. To the best of our knowledge, the effect of dimerisation on the optical spectra of L is studied here theoretically for the first time.