ABSTRACT
We have developed interatomic interaction parameters for Na+ and Cl- hydration using the dissociative water potential of Mahadevan and Garofalini [J. Phys. Chem. B 2007, 111, 8919] suitable for molecular dynamic simulations. Simulations were performed for small ion-water clusters Na(H2O)n+ (n=1-6) and Cl(H2O)m- (m=1-5), as well as dilute aqueous solutions of the ions in water, reproducing the structure and energies found in the literature. A simulation of an HCl molecule in water demonstrated the dissociation of the molecule. The Na+ and Cl- ion-ion interaction parameters also reproduce the energy and density of crystalline NaCl. A series of simulations of NaCl at progressively increasing temperatures from 300 to 1400 K produced solid densities varying by less than 1% from experiment.
Subject(s)
Chlorides/chemistry , Computer Simulation , Models, Chemical , Sodium/chemistry , Water/chemistry , Ions/chemistry , Sodium Chloride/chemistry , TemperatureABSTRACT
Nitrogen sorption at 77 K is a standard technique for the characterization of mesoporosity. However, it seemed to be unable to detect the full, theoretically expected pore volume in high-porosity aerogels. Investigating this problem, we found that if only the sample is sufficiently equilibrated upon sorption, the full pore volume is detected regardless of its porosity. As insufficient equilibration also effects the pore size distribution deduced from the isotherm, highly erroneous results can be avoided if complete equilibration upon each sorption step is assured. For compliant aerogels the effect of sample deformation during analysis has to be taken into account. Copyright 2001 Academic Press.
ABSTRACT
The residual thermal stresses in optical waveguide fibers can be large enough to cause substantial changes in the refractive-index profile and to create optical anisotropy. This paper presents a method of calculating these effects and illustrates the influence of various dopants on the magnitudes of the stresses.
