Monte Carlo simulations have been used to predict the interlayer basal separations of sodium-saturated Wyoming clays at constant stress (NPzzT ensemble) and chemical potential (μVT ensemble). These use Ewald summation technique incorporate long-range Coulombic interactions in calculation total energy pressure tensor. A comparison is made between one, two, three sheets clay. It shown that, for small separations, least two separate clay must be avoid system-size effects. The stable...

Nanocrystalline cobalt spinels were synthesized under hydrothermal conditions, starting from metal chlorides. The color properties in these systems mainly depend upon the preparative method and cation distributions, which have been determined by X‐ray powder diffraction using Rietveld refinements visible near infrared absorption spectra. We observe influence of tetrahedral octahedral preference cations such as Co 2+ , Cr 3+ Mn formation development spinel pigments. All samples prepared...

We have investigated the strongest infrared absorption mode in silicon oxide films obtained at low temperatures (anodic and plasma oxides). The asymmetric stretching transverse of Si-${\mathrm{O}}_{4}$ tetrahedra, centered 1070 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, exhibits an interesting multiple-resonance structure on high-energy side spectrum. A transverse-optical (TO) 1200 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ a longitudinal-optical (LO) 1150 both modes associated with LO-TO...

Monte Carlo grand canonical molecular simulations on the hydration of Na-, K-, and Ca-montmorillonite show that between 333 533 K 300−1300 bar Na-montmorillonite forms stable one-layer hydrates d001 spacings 12.64−12.38 Å, K-montmorillonite 12.78−12.59 12.48−12.32 Å. A two-layer hydrate 14.80 Å occurs for at 1300 bar, 15.32 14.74 2000 13.83 473 1000 bar. Three-layer may possibly form within these same ranges. Outside them, simulate as only hydrates. In sedimentary basins, will locate 6.7 km...

The hydration of Na-saturated Wyoming-type montmorillonite is investigated by Monte Carlo simulations at constant stress in the NP(zz)T ensemble and chemical potential microVT ensemble, sedimentary basin temperature 353 K pressure 625 bar, equivalent to 2-4 km depth. use procedures established Chavez-Paez et al. [J. Chem. Phys. 114, 1405 (2001)]. At these conditions, predict a single stable form 1,2-water layer Na-montmorillonite, containing 164.38 mg/g or 53.37 molecules/layer adsorbed...

Monte Carlo molecular simulations of the hydration K-saturated Wyoming-type montmorillonite at constant stress in NPzzT ensemble and chemical potential grand canonical muVT ensemble, under basin-like conditions 353 K 625 bar, show a strong tendency K+ ions to adhere siloxane surface, forming predominant inner-sphere complexes with tetrahedral oxygen atoms adsorbed water molecules. Simulations predict that none K-montmorillonite hydrates, one-, two-, three-layer are stable this environment...

Beta alumina was once considered to be merely a metastable polymorph of corundum. Its status as distinct and stable compound (Na 2 O.‐11Al O 5 analogous formulas) is now quite firmly established. Yet the published phase diagram for system soda‐alumina‐silica takes no cognizance its existence. A study alumina‐rich portion conducted determine whether or not beta should incorporated in diagram. Conventional methods investigation were used, with certain innovations designed overcome difficulties...

Cristobalite-tridymite blade nanocrystals cemented by SiO2-glass and tridymite fill separately spherules released explosive volcanism, in rhyolitic tuffs from the Province of Mesa Central, Mexico. This paper presents mineralogy silica polymorphs, occurrence, process formation Central. The understanding origin these pure SiO2-polymorphs, their association with high-temperature minerals, fractionation magmas, role volatiles contribute to our knowledge on technological implications damaging...

Abstract A random -layer disordered kaolinite from Conception de Buenos Aires, Jalisco, Mexico, gives an X-ray diffraction pattern resembling that of halloysite but has a morphology. The mineral was located in lignite deposit and, apparently formed by alteration volcanic rocks the Cenozoic, with rapid cooling and sedimentation lacustrine deposits. It is associated plagioclase, quartz, cristobalite, montmorillonite, goethite organic material. analysis purified material (44.84 per cent SiO 2 ,...

To know the geochemical behaviour of Al, Cd, Cr, Cu, Fe, Li, Mn, Ni and Zn, their sources, distribution patterns association with sedimentological factors (organic carbon carbonate contents, grain size clay mineralogy sediments), 29 surface sediment samples were collected from Mazatlan Bay, Mexico. In addition to determination concentration these variables by standard methods proposed on literature, a correlation matrix two principal component analyses (PCA) made normalisation procedure was...