Hartree–Fock geometry optimisation of periodic systems with the Crystal code

Civalleri, Bartolomeo; D’Arco, Philippe; Orlando, Roberto; Saunders, V. R.; Dovesi, Roberto

doi:10.1016/s0009-2614(01)01081-8

Cited by 302 publications

(227 citation statements)

References 24 publications

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“…Structures were optimized by using the total energy analytical energy gradients with respect to atomic coordinates and unit cell parameters [40][41][42] , within a quasi-Newton scheme combined with the BFGS algorithm for Hessian updating [43][44][45][46] . Convergence was checked on both gradient components and nuclear displacements, for which the default values 28 were chosen.…”

Section: Methodsmentioning

confidence: 99%

The Raman spectrum of CaCO3 polymorphs calcite and aragonite: A combined experimental and computational study

Pierre

Carteret

Maschio

et al. 2014

The Journal of Chemical Physics

146

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Section: Methodsmentioning

confidence: 99%

The Raman spectrum of CaCO3 polymorphs calcite and aragonite: A combined experimental and computational study

Pierre

Carteret

Maschio

et al. 2014

The Journal of Chemical Physics

146

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“…Convergence threshold on the energy for the self-consistent-field (SCF) step of the calculations was set to 10 −11 Ha for both the structure optimizations and phonon calculations. All structures were optimized by use of analytical energy gradients with respect to both atomic coordinates and unit-cell parameters (Doll 2001;Doll et al 2001;Civalleri et al 2001), with a quasi-Newton technique combined with the BFGS algorithm for Hessian updating (Broyden 1970;Fletcher 1970;Goldfarb 1970;Shanno 1970). Convergence was checked on both gradient components and nuclear displacements; the corresponding tolerances on their root mean square were chosen to be 10 times more severe than the default values, that is, 0.00003 a.u.…”

Section: Computational Details and Methodsmentioning

confidence: 99%

Thermodynamics and phonon dispersion of pyrope and grossular silicate garnets from ab initio simulations

et al. 2015

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The phonon dispersion and thermodynamic properties of Mg 3 Al 2 Si 3 O 12 , pyrope, and Ca 3 Al 2 Si 3 O 12 , grossular, have been computed by using an ab initio quantum mechanical approach, an all-electron variational Gaussian type basis set and the B3LYP hybrid functional, as implemented in the CRYSTAL program. Dispersion effects in the phonon bands have been simulated by using supercells of increasing size, containing 80, 160, 320, 640, 1280 and 2160 atoms, corresponding to 1, 2, 4, 8, 16 and 27 k points in the first Brillouin zone. Phonon band structures, density-of-states and corresponding inelastic neutron scattering spectra are reported. Full convergence of the various thermodynamic properties, in particular entropy (S) and specific heat at constant volume (C V ), with the number of k points is achieved with 27 k points. The very regular behavior of the S(T ) and C V (T ) curves as a function of the number of k points, determined by high numerical stability of the code, permits extrapolation to an infinite number of k points. The limiting value differs from the 27-k case by only 0.40% at 100 K for S (the difference decreasing to 0.11% at 1000 K) and by 0.29% (0.05% at 1000 K) for C V . The agreement with the experimental data is rather satisfactory. We also address the problem of the relative entropy of pyrope and grossular, a still debated question. Our lattice dynamical calculations correctly describe the larger entropy of pyrope than grossular by taking into account merely vibrational contributions and without invoking "static disorder" of the Mg ions in dodecahedral sites. However, as the computed entropy difference is found to be larger than the experimental one by a factor of 2-3, present calculations can not exclude possible thermally-

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“…The geometry optimization was performed by means of a quasi-Newton algorithm in which the quadratic step (BFGS Hessian updating scheme) is combined with a linear one as proposed by Schlegel. 39 The adsorption energies (E) per mole of a H atom and per unit cell were computed as:…”

Section: Methodsmentioning

confidence: 99%

Interstellar H adsorption and H₂formation on the crystalline (010) forsterite surface: a B3LYP-D2* periodic study

Navarro‐Ruiz

Sodupe

Ugliengo

et al. 2014

Phys. Chem. Chem. Phys.

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The physisorption/chemisorption of atomic hydrogen on a slab model of the Mg2SiO4 forsterite (010) surface mimicking the interstellar dust particle surface has been modeled using a quantum mechanical approach based on periodic B3LYP-D2* density functional calculations (DFT) combined with flexible polarized Gaussian type basis sets, which allows a balanced description of the hydrogen/surface interactions for both minima and attachment of H at the surface at 100 K, but prevents the same process to occur at 10 K.From this H-chemisorbed state, second hydrogen chemisorption mainly occurs on the neighboring Mg ion, thus forming a Mg-H surface group, giving rise to a surface species stabilized by favorable electrostatic interactions between the OH + /H -Mg pair. The formation of molecular hydrogen at the (010) forsterite surface adopting a LangmuirHinshelwood mechanism takes place either starting from two physisorbed H atoms with an almost negligible kinetic barrier through a spin-spin coupling driven reaction or from two chemisorbed H atoms with a barrier surmountable already at T higher than 10 K. We also suggest that a nanosized model of the interstellar dust built from a replica of the forsterite unit cell is able to adsorb half the energy released by the H2 formation by increasing its temperature by about 50 K which could then radiates in about 0.02 s.

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Hartree–Fock geometry optimisation of periodic systems with the Crystal code

Cited by 302 publications

References 24 publications

The Raman spectrum of CaCO3 polymorphs calcite and aragonite: A combined experimental and computational study

The Raman spectrum of CaCO3 polymorphs calcite and aragonite: A combined experimental and computational study

Thermodynamics and phonon dispersion of pyrope and grossular silicate garnets from ab initio simulations

Interstellar H adsorption and H₂formation on the crystalline (010) forsterite surface: a B3LYP-D2* periodic study

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Hartree–Fock geometry optimisation of periodic systems with the Crystal code

Cited by 302 publications

References 24 publications

The Raman spectrum of CaCO3 polymorphs calcite and aragonite: A combined experimental and computational study

The Raman spectrum of CaCO3 polymorphs calcite and aragonite: A combined experimental and computational study

Thermodynamics and phonon dispersion of pyrope and grossular silicate garnets from ab initio simulations

Interstellar H adsorption and H2formation on the crystalline (010) forsterite surface: a B3LYP-D2* periodic study

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Interstellar H adsorption and H₂formation on the crystalline (010) forsterite surface: a B3LYP-D2* periodic study