Approach combining the Rietveld method and pairs distribution function analysis to study crystalline materials under high-pressure and/or temperature: Application to rhombohedral Bi2Te3 phase
J. C. de Lima, Z. V. Borges, C. M. Poffo, S. M. Souza, D. M. Trichês, R. S. de Biasi
An approach combining the Rietveld method and pairs distribution function analysis to study crystalline materials under high pressure or temperature was early proposed by us, and in this study, it was applied to investigate de effect of high pressure on the rhombohedral Bi2Te3 phase. The refined structural parameters obtained from the Rietveld refinement of the XRD patterns measured for pressures up to 9.1 GPa were used as input data to simulate the partial and total structure factors SBiBi, SBiTe, STeTe, and SBi2Te3. Fourier transformation of the Sij factors permitted to obtain the partial and total pairs distribution functions GBiBi, GBiTe, GTeTe, and GBi2Te3. The first coordination shells of these Gij functions are formed by subshells and, with increasing pressure in the 1.1 to 6.3 GPa range, occur a partial separation of subshells. Also, the increase of pressure in this range promotes a drastic reduction in the values of the intralayer angles TeBiTe, and consequently, in the intralayer distance TeTe. A drastic reduction in the interlayers distance Te-Te was also observed. Several studies are reported in the literature, including one carried out by us, show the presence of an ETT in this pressure range. The obtained results suggest that the ETT is related with the decrease of the intralayer angles TeBiTe, and intra- and interlayer distance TeTe. Experimental results describing the pressure dependence the thermoelectric power, electrical resistivity, and power fator for rhombohedral Bi2Te3 are reported, and an enhancement of the power factor in the 1.1 to 6.3 GPa range is observed. The results obtained in this study give evidence that this enhancement in the power factor is related with the decrease of the intralayer angles TeBiTe, and with the decrease of intralayer- and interlayers homopolar TeTe bonds.
An approach combining the Rietveld method and pairs distribution function analysis was developed and can help to understand the effect of temperature and/or high-pressure on crystalline materials. It was applied to orthorhombic Ta2O5 compound, and the obtained results were compared with the experimental pairs distribution function reported in the literature, and an excellent agreement was reached. The approach permitted to simulate average pairs distribution functions GTa-Ta(R), GTa-O(R), and GO-O(R) and the average radial distribution functions RDFTa-Ta(R), RDFTa-O(R), and RDFO-O(R). The coor…
Results of Rietveld analysis of the synchrotron XRD data on Pb(Zr_xTi_1-x)O_3 (PZT) for 0.525\leqx\leq0.60 are presented to show the absence of rhombohedral phase on the Zr-rich side of the morphotropic phase boundary (MPB). Our results reveal that the structure of PZT is monoclinic in the Cm space group for 0.525\leq x\leq 0.60. The nature of the monoclinic distortion changes from pseudo-tetragonal for 0.525\leqx\leq0.54 to pseudo-rhombohedral for x>0.54.
The historic de Haas van Alphen effect observed in the late 1950s in CSIR-NPL by J.S. Dhillon and D. Shoenberg in pure bismuth and zinc metal is revisited in this article hrough a single crystalline phase of bismuth crystal, which is observed in terms of resistivity as predicted by Shubnikov de Haas oscillations. The occurrence of oscillations in the transverse magnetic field confirms the presence of the Fermi surface. The single crystal of bismuth is grown through solid-state reaction under an optimized heat treatment whose purity and structural phase are confirmed through XRD, SEM, and EDAX.
We present here the results of structural studies on multiferroic (1-x)Bi(Ni1/2Ti1/2)O3-xPbTiO3 solid solution using Rietveld analysis on powder x-ray diffraction data in the composition range 0.35 to 0.55. We have determined precisely the stability region of various crystallographic phases at room temperature for (1-x)Bi(Ni1/2Ti1/2)O3-xPbTiO3 . Structural transformation from pseudo-cubic to tetragonal phase is observed via phase coexistence region demarcating the morphotropic phase boundary region. The morphotropic phase boundary region consists of coexisting tetragonal and monoclinic structu…
We present here the results of the room temperature dielectric constant measurements and Rietveld analysis of the powder x-ray diffraction data on $(1-x)[Pb(Mg_{1/3}Nb_{2/3})O_3]-xPbTiO_3$(PMN-$x$PT) in the composition range $0.20 \leq x \leq 0.45$ to show that the morphotropic phase boundary (MPB) region contains two monoclinic phases with space groups Cm (or $M_B$ type) and Pm (or $M_C$ type) stable in the composition ranges $0.27 \leq x \leq 0.30$ and $0.31 \leq x \leq 0.34$, respectively. The structure of PMN-$x$PT in the composition ranges $0 \leq x \leq$ 0.26, and $0.35 \leq x \leq1$ is …
We report a comprehensive magneto-transport study on single crystalline p-type topological crystalline insulator (TCI) SnTe, across the cubic-to-rhombohedral (R3m) transition which occurs as a function of temperature. The electrical resistivity of a well-characterized SnTe crystal shows evidence for the cubic-to-rhombohedral structural transition at T$_s$ $\sim$64,K and a carrier density of $\sim$1.8$\times$10$^{20}$ at 77,K. As a function of applied magnetic field perpendicular to the (100) plane, SnTe exhibits a large unsaturated linear magnetoresistance (LMR) reaching a value of 42% at 5K a…
Controlling the crystalline structure of Hafnium Zirconate and its epitaxial relationship to a semiconducting electrode has a high technological interest, as ferroelectric materials are key ingredients for emerging electronic devices. Using Pulsed Laser Deposition, a phase pure, ultra-thin film of HfZrO4 is grown epitaxially on a GaN (0001) / Si (111) template. Since standard microscopy techniques do not allow to determine with certitude the crystalline structure of the film due to the weak scattering of oxygen, differentiated differential phase contrast (DPC) Scanning Transmission Electron Mi…
The electrical, in-plane resistance as a function of temperature $R(T)$ of bulk and mesoscopic thin graphite flakes obtained from the same batch was investigated. Samples thicker than $\sim 30$ nm show metalliclike contribution in a temperature range that increases with the sample thickness, whereas a semiconductinglike behavior was observed for thinner samples. The temperature dependence of the in-plane resistance of all measured samples and several others from literature can be very well explained between 2 K and 1100 K assuming three contributions in parallel: a metalliclike conducting path…
Two boron-rich chalcogenides B12S and B12Se isostructural to α-rhombohedral boron were synthesized by chemical reaction of the elements at high-pressure - high-temperature conditions. The crystal structures and stoichiometries of both compounds were confirmed by Rietveld refinement and elemental analysis. The experimental Raman spectra of B12S and B12Se were investigated for the first time. All observed Raman bands have been attributed to the theoretically calculated phonon modes, and the mode assignment has been performed.
The crystalline structures of superionic high temperature copper selenides Cu$_{2-x}$Se ($0 \le x \le 0.25$) produced by Mechanical Alloying were investigated using X-ray diffraction (XRD) technique. The measured XRD patterns showed the presence of the peaks corresponding to the crystalline superionic high temperature $α$-Cu$_2$Se phase in the as-milled sample, and its structural data were determined by means of a Rietveld refinement procedure. After a heat treatment in argon at 200$^\circ$C for 90 h, this phase transforms to the superionic high temperature $α$-Cu$_{1.8}$Se phase, whose struct…
Structural investigation on $Co_{3-x}Mn_xTeO_6$; ($0 \lt x \le 2$) solid solutions as a function of Mn concentration using Synchrotron X-ray diffraction (SXRD) and XANES measurements are presented. Phase diagram obtained from Rietveld Refinement on SXRD data as a function of Mn concentration indicates doping disproportionate mixing of both monoclinic (C2/c) and rhombohedral (R-3) structure (for $x \lt 0.5$) while only R-3 symmetry for $x \ge 0.5$. Furthermore, Rietveld analysis on SXRD data shows increase in lattice parameters and average transition metal oxygen (Co/Mn-O) bond lengths for $x \…
SnTe, an archetypical topological crystalline insulator, often shows a transition from a highly symmetric cubic phase to a rhombohedral structure at low temperatures. In order to achieve the highly symmetric cubic phase at low temperatures suitable for quantum behaviour, we have employed the modified Bridgman method to grow a high-quality single-crystalline sample of SnTe. Analysis of the crystal structure using Laue diffraction and rocking curve measurements show a very high degree of single crystallinity of the sample. Resistivity and the specific heat data do not show the signature of struc…
The perovskite-like ferroelectric system PbZr(1-x)Ti(x)O3 (PZT) has a nearly vertical morphotropic phase boundary (MPB) around x=0.45-0.50. Recent synchrotron x-ray powder diffraction measurements by Noheda et al. [Appl. Phys. Lett. 74, 2059 (1999)] have revealed a new monoclinic phase between the previously-established tetragonal and rhombohedral regions. In the present work we describe a Rietveld analysis of the detailed structure of the tetragonal and monoclinic PZT phases on a sample with x= 0.48 for which the lattice parameters are respectively: at= 4.044 A, ct= 4.138 A, at 325 K, and am=…
Quasi-hydrostatic compression of rhombohedral boron monosulfide (r-BS) has been studied up to 50 GPa at room temperature using diamond-anvil cells and angle-dispersive synchrotron X-ray diffraction. A fit of the experimental P-V data to the Vinet equation of state yields bulk modulus of 42.2(1.4) GPa and its first pressure derivative of 7.6(2) that are in excellent agreement with our ab initio calculations. Formation of a new high-pressure phase of boron monosulfide (hp-BS) has been observed above 35 GPa. According to ab initio evolutionary crystal structure predictions combined with Rietveld …
Active control over the shape, composition and crystalline habit of nanocrystals is a long sought-after goal. Various methods have been shown to enable post-synthesis modification of nanoparticles, including the use of the Kirkendall effect, galvanic replacement and cation or anion exchange, all taking advantage of enhanced solid-state diffusion on the nanoscale. In all these processes, however, alteration of the nanoparticles requires introduction of new precursor materials. Here we show that for cesium lead halide perovskite nanoparticles, a reversible structural and compositional change can…
For topological insulators and topological crystalline insulators (TCIs), their exotic surface states are promising for fundamental condensed matter physics research as well as future electronics such as low-dissipation electronics and spintronics. However, the high bulk carrier density that often dominates the transport property is the major materials challenge, critically hindering our ability to study and manipulate the surface states. In this manuscript, we demonstrate an alloying strategy, SnSexTe1-x, to effectively reduce the bulk carrier density. As long as SnSexTe1-x remains in the cub…
In this investigation, undoped BiFeO$_3$, Gd doped Bi$_{0.9}$Gd$_{0.1}$FeO$_3$, and Gd-Ti co-doped Bi$_{0.9}$Gd$_{0.1}$Fe$_{1-x}$Ti$_x$O$_3$ (x = 0.10, 0.20) materials were synthesized to report their multiferroic properties. The structural analysis and phase identification of these multiferroic ceramics were performed using Rietveld refinement. The Rietveld analysis has confirmed the high phase purity of the 10% Gd-Ti co-doped Bi$_{0.9}$Gd$_{0.1}$Fe$_{0.9}$Ti$_{0.1}$O$_3$ sample compared to that of other compositions under investigation. The major phase of this particular composition is of rh…
Physically-Constrained Autoencoder-Assisted Bayesian Optimization for Refinement of High-Dimensional Defect-Sensitive Single Crystalline Structure
Bredesen Center for Interdisciplinary Research, University of Tennessee, Knoxville, USA（跨学科研究中心，田纳西大学）；Center for Advanced Material Science and Manufacturing, University of Tennessee, Knoxville, TN 37996, USA（先进材料科学与制造中心，田纳西大学）；Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA（物理与天文学系，田纳西大学）；Georgia Institute of Technology, Atlanta, GA 30332, USA（佐治亚理工学院）；Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA（弗吉尼亚理工大学）；Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA（材料科学与工程系，田纳西大学）；Department of Physics and Astronomy, Institute for Quantum Matter, Johns Hopkins University, Baltimore, MD 21218（物理与天文学系，量子物质研究所，约翰霍普金斯大学）；Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218（材料科学与工程系，约翰霍普金斯大学）；The Ralph O’Connor Sustainable Energy Institute, Johns Hopkins University, Baltimore, MD 21218（罗伯特·奥康纳可持续能源研究所，约翰霍普金斯大学）；Advanced Photon Source, Argonne National Lab, Lemont, IL 60439, USA（先进光子源，阿贡国家实验室）；University of Tennessee-Oak Ridge Innovation Institute, Knoxville, TN 37996, USA（田纳西大学奥本创新研究所）
We report the synthesis of a single-phase sample of the superconducting crystalline approximant Au64.0Ge22.0Yb14.0 and present a structure model refined by Rietveld analysis for X-ray diffraction data.
Structural, magnetic, and dielectric properties of Sm$_2$CoMnO$_6$ have been studied. X-ray diffraction and Rietveld analysis show that the sample crystallizes in the monoclinic structure with \textit{P2$_1$/n} space group. Magnetic study shows that the sample undergoes a paramagnetic to ferromagnetic phase transition around $T_c$ $\sim$148 K and a low-temperature ordering of Sm$^{3+}$ moments. Temperature-dependent Raman study shows spin-phonon coupling present in this material. Dielectric response of Sm$_2$CoMnO$_6$ shows strong frequency dependence with large dispersion and large dielectric…
A simple route to prepare Gd$_{0.7}$Sr$_{0.3}$MnO$_3$ nanoparticles by ultrasonication of their bulk powder materials is presented in this article. For comparison, Gd$_{0.7}$Sr$_{0.3}$MnO$_3$ nanoparticles are also prepared by ball milling. The prepared samples are characterized by X-ray diffraction (XRD),field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscope (XPS), and Superconducting Quantum Interference Device (SQUID) magnetometer. XRD Rietveld analysis is carried out extensively for the determination of crystallographic paramete…
The evolution of the atomic structures of the combinatorial library of Sm-substituted thin film BiFeO3 along the phase transition boundary from the ferroelectric rhombohedral phase to the non-ferroelectric orthorhombic phase is explored using scanning transmission electron microscopy (STEM). Localized properties including polarization, lattice parameter, and chemical composition are parameterized from atomic-scale imaging and their causal relationships are reconstructed using a linear non-Gaussian acyclic model (LiNGAM). This approach is further extended toward exploring the spatial variabilit…
The existing controversies about the space group symmetries of Pb(ZrxTi1-x)O3 (PZT) above and below antiferrodistortive (AFD) phase transition temperature (TAFD) in the Zr4+- rich (0.620<x<0.940) compositions are addressed using the results of dielectric, synchrotron x-ray powder diffraction (SXRPD) and neutron powder diffraction (NPD) studies. These compositions undergo an AFD phase transition above room temperature due to tilting of oxygen octahedral leading to a superlattice phase of PZT. We have substituted 6% Sr2+ at Pb2+-site to enhance the tilt angle and thereby the intensity of the sup…
Polycrystalline La1-xPbxMnO3+-y (x = 0.3, 0.35, 0.4) solid solutions were prepared by solid state reaction method and their magnetic properties have been investigated. Rietveld refinement of X-ray powder diffraction patterns showed that all samples are single phase and crystallized with the rhombohedral structure in the R-3c space group. A second order paramagnetic to ferromagnetic phase transition was observed for all materials. The Griffiths phase (GP), identified from the temperature dependence of the inverse susceptibility, was suppressed by increasing magnetic field and showed a significa…
We present a new method to obtain topological insulator Bi$_2$Se$_3$ thin films with a centimeter large lateral length. To produce amorphous Bi$_2$Se$_3$ thin films we have used a sequential flash-evaporation method at room temperature. Transmission electron microscopy has been used to verify that the prepared samples are in a pure amorphous state. During annealing the samples transform into the rhombohedral Bi$_2$Se$_3$ crystalline strcuture which was confirmed using X-ray diffraction and Raman spectroscopy. Resistance measurements of the amorphous films show the expected Mott variable range …
The pressure-induced phase transition of bismuth telluride, Bi2Te3, has been studied by synchrotron x-ray diffraction measurements at room temperature using a diamond-anvil cell (DAC) with loading pressures up to 29.8 GPa. We found a high-pressure body-centered cubic (bcc) phase in Bi2Te3 at 25.2 GPa, which is denoted as phase IV, and this phase apperars above 14.5 GPa. Upon releasing the pressure from 29.8 GPa, the diffraction pattern changes with pressure hysteresis. The original rhombohedral phase is recovered at 2.43 GPa. The bcc structure can explain the phase IV peaks. We assumed that th…
Optimized growth of large-size, high quality $\text{ZrTe}_5$ single crystals enabling clear quantum oscillations in electrical transport
Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交大李政道研究所）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University（清华大学物理系低维量子物理国家重点实验室）；Frontier Science Center for Quantum Information（量子信息前沿科学中心）
Phosphorus is one of the most promising anodes for sodium ion batteries (SIBs). Little is known about the structural mechanism of Na/P cycling due to the fact that only one of the structures involved (Na3P) is crystalline. Using operando X-ray diffraction computed tomography (XRD-CT) analysed by Rietveld and pair distribution (PDF) methods combined with density functional theory (DFT) calculations we show that the sodiation and desodiation mechanisms of phosphorus are very different. Sodiation follows the thermodynamic path of lowest energy from P via NaP to Na3P while desodiation follows a ki…
By applying density functional theory (DFT) approximations, we present a first-principles investigation of elastic properties for the experimentally verified phases of a metallic perovskite LaNiO$_{3}$. In order to improve the accuracy of calculations, at first we select the most appropriate DFT approaches according to their performance in reproducing the low-temperature crystalline structure and the electronic density of states observed for the bulk LaNiO$_{3}$. Then, we continue with the single-crystal elastic constants and mechanical stability for the most common rhombohedral as well as hig…
In previous studies, we have reported that double perovskite La2NiMnO6 presents a non-negligible potential for room temperature magnetocaloric tasks. With the aim of improving even further the cooling performances and the working temperature range of double perovskites, we report the magnetic and magnetocaloric properties of La2MnFeO6 and ALaMnFeO6 (A = Sr, Ba, Ca) compounds. X-ray diffraction (XRD) and Rietveld refinement show that La2MnFeO6 (LMFO) and CaLaMnFeO6 (CLMFO) samples crystallize in an orthorhombic structure with the Pnma space group. However, a rhombohedral structure with the R3C …
The structural, dielectric and ferroelectric properties of lead-free (Na0.5-xKxBi0.5-xLax)TiO3 powders synthesized by sol-gel self-combustion method were investigated. Rietveld refinement of Synchrotron x-ray diffraction data confirms pure single phase rhombohedral crystal structure with R3c space group for all the compositions and anti-phase octahedral tilting angle decreased with increase in composition x. Homogeneity and elemental proportions were confirmed by Energy dispersive x-ray spectrometry. The temperature-dependent dielectric study has shown two diffuse type of dielectric anomaly fo…
The effect of pressure on the crystalline structure and superconducting transition temperature (Tc) of the 111-type Na1-xFeAs system using in situ high pressure synchrotron x-ray powder diffraction and diamond anvil cell techniques is studied. A pressure-induced tetragonal to tetragonal isostructural phase transition was found. The systematic evolution of the FeAs4 tetrahedron as a function of pressure based on Rietveld refinements on the powder x-ray diffraction patterns was obtained. The non-monotonic Tc(P) behavior of Na1-xFeAs is found to correlate with the anomalies of the distance betwee…
SnTe is a topological crystalline insulator that possesses spin-polarized, Dirac-dispersive surface states protected by crystal symmetry. Multiple surface states exist on the {100}, {110}, and {111} surfaces of SnTe, with the band structure of surface states depending on the mirror symmetry of a particular surface. Thus, to access surface states selectively, it is critical to control the morphology of SnTe such that only desired crystallographic surfaces are present. Here, we grow SnTe nanostructures using vapor-liquid-solid and vapor-solid growth mechanisms. Previously, SnTe nanowires and nan…
