The density of states and band gap of liquid water by sequential Monte Carlo/Quantum mechanics calculations

Couto, P. Cabral do; Guedes, Rita C.; Cabral, Benedito J. Costa

doi:10.1590/s0103-97332004000100007

Cited by 21 publications

(12 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A large gap means that high-energy radiation, such as UV, is required to do this. A small gap means that lower-energy radiation, such as green or even red light, is needed [51]. The link between the HOMO-LUMO gap and the electronic properties of the molecule have also been investigated [51].…”

Section: Electronic Propertiesmentioning

confidence: 99%

See 1 more Smart Citation

Quantum chemical investigations aimed at modeling highly efficient zinc porphyrin dye sensitized solar cells

et al. 2012

View full text Add to dashboard Cite

Zinc tetraphenylporphyrin (ZnTPP) was modified by a push-pull strategy and then density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed for the resulting derivatives. The smallest HOMO-LUMO energy gaps were found in ZnTPP-6 and ZnTPP-7, which had nitro substituents and a conjugated chain, while the largest was observed for ZnTPP-5. The energy gaps of all of the systems designed in this work were smaller than that of ZnTPP. Clear intramolecular charge transfer was observed from donor to acceptor in ZnTPP-6 and ZnTPP-7, which had nitro groups at positions R8, R9, and R10, as well as in ZnTPP-3 and ZnTPP-4, which had cyano groups at those positions. The narrow band gaps (compared to that of ZnTPP) of these designed systems, where the LUMO is above the conduction band of TiO(2) and the HOMO is below the redox couple, indicate that they are efficient sensitizers. The B bands of these newly designed derivatives, except for ZnTPP-5, are redshifted compared with the B band of ZnTPP.

show abstract

Section: Electronic Propertiesmentioning

confidence: 99%

“…A small gap means that lower-energy radiation, such as green or even red light, is needed [51]. The link between the HOMO-LUMO gap and the electronic properties of the molecule have also been investigated [51]. A smaller energy gap leads to a redshift in the absorption spectrum [52].…”

Section: Electronic Propertiesmentioning

confidence: 99%

Quantum chemical investigations aimed at modeling highly efficient zinc porphyrin dye sensitized solar cells

et al. 2012

View full text Add to dashboard Cite

show abstract

“…For example, the dispersion component of the interaction energy for snapshot 2 of the catechol molecule in Figure 5 is −19.1 kcal/mol. Cabral do Couto et al 48 have also used shells of quantum water molecules surrounded by electro- static embedding charges in order to reduce the undesired surface effects when studying the electronic properties of a water molecule in bulk water. A further measure of the performance of the embedding approach can be provided by investigation of its effect on atomic charges, which are indicators of the chemical environment that the atoms experience.…”

Section: Solvent-ligand Interactionsmentioning

confidence: 99%

Electrostatic embedding in large-scale first principles quantum mechanical calculations on biomolecules

Fox

Pittock

Fox

et al. 2011

The Journal of Chemical Physics

View full text Add to dashboard Cite

Biomolecular simulations with atomistic detail are often required to describe interactions with chemical accuracy for applications such as the calculation of free energies of binding or chemical reactions in enzymes. Force fields are typically used for this task but these rely on extensive parameterisation which in cases can lead to limited accuracy and transferability, for example for ligands with unusual functional groups. These limitations can be overcome with first principles calculations with methods such as density functional theory (DFT) but at a much higher computational cost. The use of electrostatic embedding can significantly reduce this cost by representing a portion of the simulated system in terms of highly localised charge distributions. These classical charge distributions are electrostatically coupled with the quantum system and represent the effect of the environment in which the quantum system is embedded. In this paper we describe and evaluate such an embedding scheme in which the polarisation of the electronic density by the embedding charges occurs self-consistently during the calculation of the density. We have implemented this scheme in a linear-scaling DFT program as our aim is to treat with DFT entire biomolecules (such as proteins) and large portions of the solvent. We test this approach in the calculation of interaction energies of ligands with biomolecules and solvent and investigate under what conditions these can be obtained with the same level of accuracy as when the entire system is described by DFT, for a variety of neutral and charged species.

show abstract

“…They are not understood quite in comparison with thermodynamics and structure of water, but they are very important for understanding water as participant and medium of chemical reactions. This medium is described as a dielectric with the broad band gap, g=6.9 eV [2] as a difference between electron energies at the top of valence band or a highest occupied molecular orbital and the bottom of conduction band as a lowest unoccupied molecular orbital. At the same time, there are two allowed local electron states in the band gap of liquid water such as an occupied-by-electron level, ε OH , of hydroxide ion, OH , and the vacant one of hydroxonium cation, ε H3O + , located symmetrically nearby the band-gap middle with the energy difference between them of 1.75 eV [3].…”

Section: Introductionmentioning

confidence: 99%

On Electrochemical Managing the Properties of Aqueous Coolant

Alexander¹

2017

Mod Chem Appl

View full text Add to dashboard Cite

Liquid water as a chemical compound with the wide band gap is characterized by varying their Fermi level as a linear identifier of water oxidation-reduction potential (ORP). This potential is the management tool for changing chemical properties of the aqueous coolant by forced shifting Fermi level in the band gap at the expense of insignificant deviation (|z|<10) of water composition, H 2 O 1-z , from the stoichiometric one (z=0). The hypo-stoichiometric state (z>0) with the negative ORP is realized when Fermi level is shifted to the local donor level, ε HO , by electro-reducing the aqueous coolant in the electrochemical cell with the strongly polarized anode and the quasi-equilibrium cathode, occupying εH 2 O by electrons, and forming hydroxonium radicals, H 3 O, as the strongest reducers. Opposite, the hyperstoichiometric state (z<0) with the positive ORP is realized in the electrochemical cell with the strongly polarized cathode and the quasi-equilibrium anode when Fermi level is shifted to the local acceptor level, radicals, ε OH , as the strongest oxidizers. ε OH , forming in water hydroxyl.

show abstract

The density of states and band gap of liquid water by sequential Monte Carlo/Quantum mechanics calculations

Cited by 21 publications

References 29 publications

Quantum chemical investigations aimed at modeling highly efficient zinc porphyrin dye sensitized solar cells

Quantum chemical investigations aimed at modeling highly efficient zinc porphyrin dye sensitized solar cells

Electrostatic embedding in large-scale first principles quantum mechanical calculations on biomolecules

On Electrochemical Managing the Properties of Aqueous Coolant

Contact Info

Product

Resources

About