THE LOW-TEMPERATURE AND HIGH-PRESSURE THERMOELASTIC AND STRUCTURAL PROPERTIES OF CHALCOPYRITE, CuFeS2

Abstract

The thermoelastic properties of a sample of chalcopyrite from the Palabora mine, South Africa, have been investigated in the temperature range 4.2-330 K at ambient pressure, and between 0.22 and 6.81 GPa at ambient temperature. Magnetization measurements indicated a transition to a second antiferromagnetically ordered phase in the region of 53 K; however, all attempts to characterize this magnetic phase by introducing an ordered moment onto the copper site were unsuccessful owing to the small magnitude of the refined magnetic moment. In agreement with other low-temperature crystallographic measurements made on non-antiferromagnetically ordered adamantine-structured semiconducting materials (group IV; I-VII, II-VI, III-V, I-III-VI 2 , II-IV-V 2 compounds), chalcopyrite exhibits negative linear and volumetric thermal expansion over a significant temperature interval. Calculation of the speeds of sound for a number of high-symmetry wave vectors is consistent with Blackman's model for negative thermal expansion. The unit-cell volume and isochoric heat-capacity have been fitted assuming a two-term Debye internal energy function, with consistent values being found for the two characteristic temperatures. The temperature dependence of the thermodynamic Grüneisen parameter shows a deep minimum of ~-3 at T/u 0 ~0.55 (u 0 is the Debye temperature at 0 K) and a high-temperature limit of ~0.7; these results are the first demonstration that a chalcopyrite-structured phase behaves in the characteristic manner of the simpler adamantine-structured semiconducting materials. No systematic variation in either the nuclear nor the magnetic structure was found between 4.2 and 330 K, and the vibrational Debye temperatures derived by fitting the temperature dependence of the isotropic atomic displacement parameters show no relationship to features in the phonon density of states function. The bulk modulus of chalcopyrite is 77(2) GPa, in good agreement with that determined by ab initio calculations and a recent X-ray-diffraction study, and its pressure derivative is 2.0(6). At high pressure, chalcopyrite remains antiferromagnetically ordered until 6.7(2) GPa, at which point a transition to an amorphous phase is observed. Slow decompression of this phase leads to only a limited recovery of the crystalline phase.

Colloidal CuFeS2 Nanocrystals: Intermediate Fe d-Band Leads to High Photothermal Conversion Efficiency

“… 45 The reaction led to dark purple colloidal dispersions of chalcopyrite NCs, as shown in Figure 1 , panel a. The phase purity of the as-synthesized CuFeS 2 NCs was ascertained through XRD and azimuthally integrated SAED patterns, as shown in Figure 1 , panel b, which confirmed the tetragonal (I4̅2d) crystal structure as reported for the bulk structure by Knight et al 4 …”

Low temperature thermoelastic and structural properties of LaGaO3 perovskite in the Pbnm phase

“…Clearly as both functions relate to a Debye internal energy, the characteristic temperature for a given phase should be a constant, independent of the whether the molar volume or the isochoric heat capacity is being fitted to these expressions. Knight and co-workers have shown that the Debye temperatures for CaTiO 3 [32], jadeite, NaAlSi 2 O 6 [38], and chalcopyrite, CuFeS 2 [39], derived by fitting the unit cell volumes and isochoric heat capacities independently, are close, but for a consistent evaluation of the characteristic temperature(s), within a Debye approximation, these expressions should be fitted simultaneously.…”

Effect of Cu2+ activation on interfacial water structure at the sphalerite surface as studied by molecular dynamics simulation

“…Because sphalerite and chalcopyrite have the same crystal structure, a chalcopyrite crystal structure with the Fe atoms substituted by Zn was used as the initial crystal structure of copper-zinc sulfide-CuZnS 2 . The chalcopyrite crystal lattice parameters are from a previous X-ray Diffraction (XRD) study of chalcopyrite (Knight et al, 2011). This initial copper--zinc sulfide-CuZnS 2 crystal structure is set as the input for the DFT quantum chemical calculation to get crystal geometry optimized by energy minimization.…”