: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

https://www.geology.cwu.edu/facstaff/huerta/g501/pdf/Chopin2003EPSL.pdf

Ultrahigh-pressure metamorphism: tracing continental crust into the mantle

The whole range of organic-inorganic hybrid materials are generally molded into specifically designed devices with fascinating properties that are precisely controlled. The mimicking of the processes involved in biomineralization may provide new approaches to the fabrication of specialized organic-inorganic hybrid materials. Recently, researchers found that the control over polymorphism, crystallographic orientation, and crystal organization are paramount in determining the properties of hybrid materials. In this article, the biomimetic synthesis of calcium carbonate, the most abundant biomineral, has been the main focus.

Biomimetic CaCO3 mineralization using designer molecules and interfaces

Vaterite mesocrystals with hexagonal morphology and uniform size have been successfully synthesized in the presence of a N-trimethylammonium derivative of hydroxyethyl cellulose via aggregation-mediated crystallization using a simple gas-diffusion method. The uniform hexagonal plates display sharp facets and edges, even though they are formed by the aggregation of nanocrystals. The results demonstrate that each vaterite plate can be explained as consisting of aggregates of nanoparticles that share the same three-dimensional orientation. A mechanism for the formation of hexagonal vaterite mesocrystals made of primary nanoparticles and hexagonal units is also presented. An understanding of the mesoscale transformation process will be helpful in controlling the aggregation-driven formation of complex higher-order structured materials and will provide new insights into biomineralization mechanisms. For example, the spines of sea urchins can be discussed within the framework of the mesocrystal concept. This study could provide an additional tool for designing advanced materials and could be used for the synthesis of more complex crystalline three-dimensional structures.

Uniform hexagonal plates of vaterite CaCO3 mesocrystals formed by biomimetic mineralization

-- Part C: 1. The continuum approach to crystal interfaces: basics. I: Theoretical framework. 2. Operators for orientation-dependent parameters. 3. Mechanics and thermodynamics of interfaces. 4. Equilibrium structures of junctions, edges and vertices. 5. Growth: kinematic wave theory revisited. 6. Kinetic behaviour of junctions, edges and vertices. 7. Structural phase transitions of a crystal surface as a branch of soliton physics. 8. Miscellaneous topics. II: Growth rate functions. 9. Analytic representations of R(n,A) functions. 10. Nonlinear networks and the 'assembled function' notation. 11. Physical aspects of assembling operations. 12. The systematic construction of R(n,A) functions by a sequence of assembling steps. 13. Notes on sphere-growth experiments. 14. Summary: Conclusions and outstanding questions. References. List of symbols, abbreviations and notations.

Morphology of crystals

Calcite crystals were nucleated and grown from supersaturated aqueous solutions in the presence of variable concentrations of lithium The diagram of supersaturation vs [Li+]/[Ca2+] concentration r

Morphology of Calcite (CaCO3) Crystals Growing from Aqueous Solutions in the Presence of Li+ Ions. Surface Behavior of the {0001} Form

The theoretical and equilibrium morphology of gypsum (CaSO4·2H2O) is reassessed, starting from the historical papers by Simon and Bienfait (1965) and by Heijnen and Hartman (1991). The surface profiles of the most frequently observed crystal forms have been determined following two ways: in the first one we used the Hartman−Perdok method based on the periodic bond chain (PBC) analysis, while in the second one the profile of each face was obtained using the GDIS program. In both cases, the calculation of the specific surface energy values has been made using the general utility lattice program (GULP) code. From the synthesis of the two methods, a new and much more isotropic equilibrium shape is calculated, in the case of both unrelaxed and relaxed surfaces. Further, and for the first time, beyond the well-known and singular {010}, {120}, {011}, and {111} F-forms, two stepped, {100} and {122}, and one kinked form, {102}, are found to build the equilibrium shape of gypsum.

Theoretical Equilibrium Morphology of Gypsum (CaSO4·2H2O)- 1. A Syncretic Strategy to Calculate the Morphology of Crystals

This paper deals with several properties of calcite crystals. First, the solvated surface energies at 0 K of the {1014}, {1010}, {1120}, {0118}, {0112}, {0001}, and {2134} forms were determined by means of the COSMIC method. We find that the presence of water reduces by ∼7–14% the dry surface energy at 0 K, in a homogeneous way. The solvated and dry equilibrium shapes at 0 K result to be nearly homothetic: in both cases the {1014}, {1010}, {0112}, and {0001} forms are present. In a second part of the paper, the free energy at 300 K of the most widely studied {1014}/water interface has been determined (γ(1014)/w300 K = 0.412 ± 0.020 J/m2) by combining simple thermodynamic relations and contact angle measurements. Some considerations on the free energy of other interfaces:{1010}, {1120}, {0118}, {0112}, {0001}, and {2134} are also proposed. We show that our results are consistent with thermodynamic constraints and fit quite well the known dependence of the solubility of calcite on grain size...

New Estimates of the Free Energy of Calcite/Water Interfaces for Evaluating the Equilibrium Shape and Nucleation Mechanisms

The “Four Twin Laws of Calcite”, expressed by their twin planes (10.4, 01.8, 01.2 and 0.01, hexagonal frame) have been investigated in order to assess the structure of the interfaces between twinne...

Marco Rubbo

Papers

Morphology of Calcite (CaCO3) Crystals Growing from Aqueous Solutions in the Presence of Li+ Ions. Surface Behavior of the {0001} Form

Theoretical Equilibrium Morphology of Gypsum (CaSO4·2H2O)- 1. A Syncretic Strategy to Calculate the Morphology of Crystals

New Estimates of the Free Energy of Calcite/Water Interfaces for Evaluating the Equilibrium Shape and Nucleation Mechanisms

(10.4), (01.8), (01.2), and (00.1) Twin Laws of Calcite (CaCO3): Equilibrium Geometry of the Twin Boundary Interfaces and Twinning Energy

{100} and {111} forms of the NaCl crystals coexisting in growth from pure aqueous solution