Density functional theory calculations and classical molecular dynamics simulations have been use... more Density functional theory calculations and classical molecular dynamics simulations have been used to investigate the structure and dynamics of water molecules on kaolinite surfaces and confined in the interlayer of a halloysite model of nanometric dimension. The first technique allowed us to accurately describe the structure of the tetrahedral-octahedral slab of kaolinite in vacuum and in interaction with water molecules and to assess the performance of two widely employed empirical force fields to model water/clay interfaces. Classical molecular dynamics simulations were used to study the hydrogen bond network structure and dynamics of water adsorbed on kaolinite surfaces and confined in the halloysite interlayer. The results are in nice agreement with the few experimental data available in the literature, showing a pronounced ordering and reduced mobility of water molecules at the hydrophilic octahedral surfaces of kaolinite and confined in the halloysite interlayer, with respect to water interacting with the hydrophobic tetrahedral surfaces and in the bulk. Finally, this investigation provides new atomistic insights into the structural and dynamical properties of water-clay interfaces, which are of fundamental importance for both natural processes and industrial applications.
The journal of physical chemistry. A, Jan 10, 2015
The performance of a method is generally measured by an assessment of the errors between the meth... more The performance of a method is generally measured by an assessment of the errors between the method's results and a set of reference data. The prediction uncertainty is a measure of the confidence that can be attached to a method's prediction. Its estimation is based on the random part of the errors not explained by reference data uncertainty, which implies an evaluation of the systematic component(s) of the errors. As the predictions of most density functional approximations (DFA) present systematic errors, the standard performance statistics, such as the mean of the absolute errors (MAE or MUE), cannot be directly used to infer prediction uncertainty. We investigate here an a posteriori calibration method to estimate the prediction uncertainty of DFAs for properties of solids. A linear model is shown to be adequate to address the systematic trend in the errors. The applicability of this approach to modest-size reference sets (28 systems) is evaluated for the prediction of ...
A computational protocol that combines periodic and QM/QM&amp... more A computational protocol that combines periodic and QM/QM' calculations has been applied to investigate the structural (geometrical and electronic) and photophysical absorption properties of the salicylidene aniline (SA) thermochromic molecular crystal. The protocol consists of three different steps, namely (i) the description of the molecular crystal using a periodic approach taking into account dispersion interactions, (ii) the identification of reliable finite models (clusters), and (iii) the calculation of vertical transition energies including environmental effects through the use of an electronic embedding model (QM/QM' ONIOM approach). The encouraging results obtained in this work for the β polymorph of SA, both in terms of accuracy and computational cost, open the way to the simulation and the prediction of the photophysical behavior of other molecular crystals, especially those much less well characterized experimentally.
Density functional theory calculations and classical molecular dynamics simulations have been use... more Density functional theory calculations and classical molecular dynamics simulations have been used to investigate the structure and dynamics of water molecules on kaolinite surfaces and confined in the interlayer of a halloysite model of nanometric dimension. The first technique allowed us to accurately describe the structure of the tetrahedral-octahedral slab of kaolinite in vacuum and in interaction with water molecules and to assess the performance of two widely employed empirical force fields to model water/clay interfaces. Classical molecular dynamics simulations were used to study the hydrogen bond network structure and dynamics of water adsorbed on kaolinite surfaces and confined in the halloysite interlayer. The results are in nice agreement with the few experimental data available in the literature, showing a pronounced ordering and reduced mobility of water molecules at the hydrophilic octahedral surfaces of kaolinite and confined in the halloysite interlayer, with respect to water interacting with the hydrophobic tetrahedral surfaces and in the bulk. Finally, this investigation provides new atomistic insights into the structural and dynamical properties of water-clay interfaces, which are of fundamental importance for both natural processes and industrial applications.
The journal of physical chemistry. A, Jan 10, 2015
The performance of a method is generally measured by an assessment of the errors between the meth... more The performance of a method is generally measured by an assessment of the errors between the method's results and a set of reference data. The prediction uncertainty is a measure of the confidence that can be attached to a method's prediction. Its estimation is based on the random part of the errors not explained by reference data uncertainty, which implies an evaluation of the systematic component(s) of the errors. As the predictions of most density functional approximations (DFA) present systematic errors, the standard performance statistics, such as the mean of the absolute errors (MAE or MUE), cannot be directly used to infer prediction uncertainty. We investigate here an a posteriori calibration method to estimate the prediction uncertainty of DFAs for properties of solids. A linear model is shown to be adequate to address the systematic trend in the errors. The applicability of this approach to modest-size reference sets (28 systems) is evaluated for the prediction of ...
A computational protocol that combines periodic and QM/QM&amp... more A computational protocol that combines periodic and QM/QM' calculations has been applied to investigate the structural (geometrical and electronic) and photophysical absorption properties of the salicylidene aniline (SA) thermochromic molecular crystal. The protocol consists of three different steps, namely (i) the description of the molecular crystal using a periodic approach taking into account dispersion interactions, (ii) the identification of reliable finite models (clusters), and (iii) the calculation of vertical transition energies including environmental effects through the use of an electronic embedding model (QM/QM' ONIOM approach). The encouraging results obtained in this work for the β polymorph of SA, both in terms of accuracy and computational cost, open the way to the simulation and the prediction of the photophysical behavior of other molecular crystals, especially those much less well characterized experimentally.
Uploads