Controlling the growth of the polymorphs of calcium carbonate is important in understanding the changing environmental conditions in the oceans. Aragonite is the main polymorph in the inner shells of marine organisms, and can be readily converted to calcite, which is the most stable polymorph of calcium carbonate. Both of these polymorphs are significantly more stable than vaterite, which is th...

The crystal structure of the title compound, C(16)H(13)ClO(2) (II), (space group P2(1)/c,) is a polymorph of the structure, (I), reported by Harrison, Yathirajan, Sarojini, Narayana & Indira [Acta Cryst. (2006), E62, o1647-o1649] in the ortho-rhom-bic space group Pna2(1). The dihedral angle between the mean planes of the 4-chloro- and 4-meth-oxy-substituted benzene rings is 52.9 (1)° in (II) co...

Cubic strontium manganese oxide is an end-member of the colossal magnetoresistive (CMR) family of manganese-based perovskites, Ln1-xAExMnO3. Because normal synthesis conditions lead to the 4-H hexagonal polymorph, high-pressure conditions are typically used to obtain the cubic perovskite polymorph. In this work, we describe the synthesis and structural/physical characterization of the cubic per...

A hexagonal polymorph (a = 79 A) of OmpF matrix porin from Escherichia coli spontaneously transforms to a rectangular form (a = 79 A, b = 137 A) after several months' storage in the refrigerator. Nucleation of this second polymorph is first disclosed by diffuse streaks in electron diffraction patterns or in computer-generated Fourier transforms of electron microscope images. With time, this str...

A monoclinic polymorph of theophylline, C(7)H(8)N(4)O(2), has been obtained from a chloro-form/methanol mixture by evaporation under ambient conditions. The new polymorph crystallizes with two mol-ecules in the asymmetric unit. The structure features inter-molecular N-H⋯O hydrogen bonds, resulting in the formation of dimers between two crystallographically different mol-ecules; each mol-ecule a...

The crystal structure of the title compound, C(12)H(11)NO(2), represents a new ortho-rhom-bic polymorph II of the previously reported ortho-rhom-bic form I [Zhang et al. (2009 ▶) Acta Cryst. E65, o3160]. In polymorph II, the six-membered rings form a dihedral angle of 13.8 (1)° [71.6 (1)° in I], and O-H⋯N hydrogen bonds link mol-ecules into chains along [100], whereas the crystal structure of I...

The title compound, [MgBr2(C4H8O)4] (1a), forms twinned four-component monoclinic crystals as a new polymorph, space group P21/n with Z′ = 2, in addition to the already known tetragonal polymorph (1b). Although the molecular parameters in the two polymorphs match very well, the packing patterns are significantly different. Furthermore, the correct constitution of the mixed halide bromo-chloro-t...

a new polymorph crystalline silica composition having uniform pore dimensions were synthesized by calcining a crystalline hydrated alkyl-ammonium silicate. the pore dimensions approximately were 6 angstrom for silicalite-1 and 11 angstrom for silicalite-2 units. the silicalite-1 was prepared hydrothermally at a ph of about 10 from a reaction mixture consist of water, amorphous silica and a quat...

We explore the effects of particle size and solvent environment on the thermodynamic stability of two pairs of polymorphs subjected to ball-mill neat grinding (NG) and liquid assisted grinding (LAG). Two systems were studied: (i) forms I and II of a 1 : 1 theophylline : benzamide cocrystal and (ii) forms A and B of an aromatic disulfide compound. For both systems, the most stable-bulk polymorph...