Synthesis and in-depth structure determination of a novel metastable high-pressure CrTe3 phase

High-pressure/high-temperature experiments using monoclinic CrTe3 as a starting phase result in a novel structural polymorph identified as CrTe3 (P2/m) using synchrotron X-ray diffraction and transmission electron microscopy. The magnetic properties of the novel phase were investigated through temperature- and field-dependent magnetization measurements and correlated with auxiliary theoretical investigations by first-principles electronic structure calculations and Monte Carlo simulations.


Figure S1 :
Figure S1: High-PT cell assembly applied for the in situ synchrotron diffraction experiments at the ESRF.(a) Cross section of the octahedral high-PT cell, in which Cr2O3-doped MgO was used as the pressure transmitting medium.(b) Configuration of the multi-anvil assembly consisting of WC anvils equipped with pyrophyllite gaskets with boron windows in beam direction.The WC anvils compress the octahedral pressure cell.

Figure S2 :
Figure S2: Powder X-ray diffraction data of a high pressure synthesized CrTe 3 powder pellet measured at the Powder Diffraction and Total Scattering Beamline P02.1 (PETRA III / DESY).The shown fit of the Rietveld refinement is a possible crystal structure solution in space group Pnn2 for a stoichiometry of CrTe 2 .First reflections are not included for this crystal structure model and reflections at higher diffraction angles are not well fitted.R wp for this model is 7.221 %.

Figure S3 :
Figure S3: Powder X-ray diffraction data of a high pressure synthesized CrTe 3 powder pellet measured at the Powder Diffraction and Total Scattering Beamline P02.1 (PETRA III / DESY).The shown fit of the Rietveld refinement is a possible crystal structure solution in space group P2 1 /m for a stoichiometry of CrTe 4 .The intensity of the first small reflections is clearly overestimated in addition to the reflections at higher diffraction angles which are not well fitted.Furthermore, the model creates intensity for reflections which are not observable in the experimental data.R wp for this model is 7.300 %.

Figure S4 :
Figure S4: Powder X-ray diffraction data of a high pressure synthesized CrTe 3 powder pellet measured at the Powder Diffraction and Total Scattering Beamline P02.1 (PETRA III / DESY).The shown fit of the Rietveld refinement is a possible crystal structure solution in space group P2/m for a stoichiometry of CrTe 4 .The intensity of the first small reflections is clearly overestimated in addition to the reflections at higher diffraction angles which are not well fitted.R wp for this model is 7.651 %.

Figure S5 :
Figure S5: Powder X-ray diffraction data of a high pressure synthesized CrTe 3 powder pellet measured at the Powder Diffraction and Total Scattering Beamline P02.1 (PETRA III / DESY).The shown fit of the Rietveld refinement is the final crystal structure solution in space group P2/m with isotropic displacement parameters for the atomic positions for a stoichiometry of CrTe 3 .The intensity of the first small reflections is slightly overestimated in addition to the reflections at higher diffraction angles which are not well fitted.R wp for this model is 6.167 %.

Figure S6 :
Figure S6: a) Possible crystal structure solution in space group Pnn2 for a stoichiometry of.Columns of edge-sharing CrTe 6 octahedra are interconnected by common corners.Stoichiometry of CrTe 2 .b) Structure solution of CrTe 3 (P2/m).This structure represents the anisotropically refined solution of the partially filled CrTe 4 to fit the stoichiometry.The partially occupied Cr position is shown within semitransparent octahedra.The projection along the crystallographic b-axis shows the similarities to the CrTe 2 Pnn2.c) Possible crystal structure solution in space group P2/m for a stoichiometry of CrTe 4 .This solution was derived from the P2 1 /m model, see text.A view along the crystallographic b-axis shows that there is no connection between the columns of CrTe 6 octahedra.

Figure S7 :
Figure S7: STEM EDX maps showing multiple grains of the quenched high-pressure phase of CrTe 3 .The individual chemical composition of the grains denoted as A-C are summarized in TableS1of the supporting information.The enlarged frame shows a grain boundary area containing separation into Cr-and Te-rich regions.

Figure S8 :
Figure S8: Recorded PED pattern and simulated patterns of the proposed models for CrTe 2 , CrTe 3 and CrTe 4

Figure S9 :
Figure S9: experimental PEDs compared to simulations of the monoclinic CrTe 3 .The Comparison shows that the initial powder is not completely transformed into the high-pressure phase.

Figure S10 :
Figure S10: a) Crystal structure and regarding Dr. Probe simulation of the HAADF and ABF image in [010] and [100] direction with the view at the stacked partially occupied or empty Cr2 position in blue.In b) are the corresponding intensity profiles shown along the marked line.

Table S1 :
EDX quantification statistics of the powder measured in SEM and the EDX quantifications of the grains depicted in the cross-section STEM images micrographs of Figure5.