Ab initio total energy studies of minerals using density functional theory and the local density approximation

Abstract

Ab initio total energy calculations based on the local density approximation (LDA) and using a conjugategradient solver for the Kohn-Sham equations have been performed for cordierite, brucite, (Mg(OH)e) and diaspore (A1OOH). The calculated fractional coordinates of all structures are in good agreement with experimental diffraction data. The angle of the non-linear hydrogen bond in diaspore is reproduced well. The Raman active OH stretching frequency in brucite has been calculated using the frozen phonon approach and the calculated stretching frequency is in very good agreement with the observed value. The energetically most favourable calculated orientation of the proton-proton vector of an HeO molecule incorporated in the structural channels of cordierite agrees with findings deduced from spectroscopic data, and the calculated energy of hydration is in reasonable agreement with calorimetric data. It is therefore concluded that ab initio total energy calculations can confidently be used to predict properties of hydrogen bonded structures, which is difficult with conventional parameterized static lattice energy minimization calculations. An extension to the model is necessary to improve the agreement of the predicted to the observed lattice parameters for small structures.I~YWORDS: total energy calculations, local density approximation, bmcite, diaspore, cordierite, hydrogen bond, CASTEP.

An inelastic incoherent neutron scattering study of water in small-pored zeolites and other water-bearing minerals

“…Calculations of the librational dynamics of water and OH previous to our own ab initio study 11 include a molecular mechanics study of natrolite: 17,18 a study of cation-water clusters 19 and a study of the wagging of single OH bonds in brucite. 20 In this study, for the small-pored zeolites natrolite, 21,22 scolecite, 23 and wairakite, 24 and for the sheet silicate apophyllite, 25 There also exist zeolites where there is a well-defined water-water hydrogen-bonding configuration, which is fully ordered. In this study, we present the spectrum for the zeolite bikitaite Li 2 …”

Effect of exchangeable cation on the swelling property of 2:1 dioctahedral smectite—A periodic first principle study

“…The methodology has been used in mineralogy to examine the hydration of corderite. 42 Becke-Perdew parametrization 43,44 of the exchange-correlation functional, which includes gradient correction ͑GGA͒, was employed, as this is a wellestablished technique. 45,46 The pseudopotentials are constructed from the CASTEP database.…”

Anharmonic OH vibrations in brucite: Small pressure-induced redshift in the range 0-22 GPa

“…Those of particular relevance to the current study are the Mg(OH) 2 ab initio calculations of Baranek et al (2001) andD'Arco et al (1993), as well as the ab initio, B3LYP and DFT calculations of and Ugliengo et al (2004), and the DFT calculations by Winkler et al (1995) and by Reynard and Caracas (2009).…”