A monoclinic polymorph of 1-(4-chloro­phen­yl)-3-(4-methoxy­phen­yl)prop-2-en-1-one

The crystal structure of the title compound, C16H13ClO2 (II), (space group P21/c,) is a polymorph of the structure, (I), reported by Harrison, Yathirajan, Sarojini, Narayana & Indira [Acta Cryst. (2006), E62, o1647–o1649] in the ortho­rhom­bic space group Pna21. The dihedral angle between the mean planes of the 4-chloro- and 4-meth­oxy-substituted benzene rings is 52.9 (1)° in (II) compared to 21.82 (6)° for polymorph (I). The dihedral angles between the mean planes of the prop-2-en-1-one group and those of the 4-chloro­phenyl and 4-methoxy­phenyl rings are 23.3 (3) and 33.7 (1)°, respectively. in (II). The corresponding values are 17.7 (1) and 6.0 (3)°, respectively, in polymorph (I). In the crystal, weak C—H⋯π inter­actions are observed

Effect of Nb doping at Mn site on thermal expansion of Pr 0.7 Sr

a b s t r a c t In this study we present results on effect of Nb doping on thermal expansion of Pr 0.7 Sr 0.3 MnO 3 . Thermal expansion measurements were done using three terminal capacitance method. The pure sample shows a jump at the insulator-metal (I-M) transition temperature, and with Nb doping, a fourfold decrease in the jump is found. Since thermal expansion is a bulk property, this suggests that the dopants are not in the form of local clusters; rather they are distributed uniformly throughout the sample. Temperature variation of Gruniesen ratio α/C P shows that for temperatures below I-M transition, the ratio is weakly dependent on temperature. Pressure dependence on the transition temperature, dT P /dP and jump in compressibility, Δβ, of these samples has been estimated using well-known Ehrenfest equations. The present results are in fairly good agreement with those reported in the literature

Variation in the electronic, mechanical, and structural properties among the polymorphs of bismuth ferrite: a first-principles approach

Bismuth ferrite has been under intense research for many years as it can exhibit first- and second-order transitions where all the phases have distinct properties encapsulating various exciting phenomena. This work reports a computational study of bismuth ferrite and its varied phases using density functional theory with the implementation of Hubbard correction for increased accuracy. The proposed method is validated through Linear Response Theory using Quantum ESPRESSO. The phase transition and the mechanical properties are explored by calculating elastic tensors for different polymorphs. A negative Poissons ratio for the tetragonal phase supporting its growth in compressive environments is predicted. The electronic properties of different phases of bismuth ferrite are explored, which helps in understanding properties such as charge transfer excitation, metal-insulator transition, ferroelectric nature based on lone pair charges and orbital hybridization. The phonon modes of different phases are also investigated.Funding Agencies|Manipal Academy of Higher Education (MAHE), Manipal, India</p