To the Stability of Janus Phases in Layered Trichalcogenide MPX₃ Crystals: Insights from Experiments and Theory

Abstract

The stability and electronic structure of the possible Janus phase for the representative example of transition metal trichalcogenide FePS 1.5 Se 1.5 crystals are studied and discussed. The respective stoichiometric layered parent (FePS 3 and FePSe 3 ) and mixed (FePS 1.5 Se 1.5 ) compounds are successfully synthesized, and our experimental data confirm the high quality of the obtained crystals and the uniform random distribution of S and Se atoms in the chalcogens' layers for the FePS 1.5 Se 1.5 crystals. These results are supported by the detailed density functional theory calculations, which indicate the absence of the Janus phase for the layered 3D FePS 1.5 Se 1.5 . This effect is explained by the large uncompensated dipole moment for the Janus phase, and the possible routes for the stabilization of 2D FePS 1.5 Se 1.5 Janus layers are discussed.

Dual Character of the Insulating State in the van der Waals Fe1–xNixPS3 Alloyed Compounds

“…According to these data only (00 l ) diffraction peaks are visible in the XRD spectra confirming the high crystallographic ordering of all samples. The ratio of the intensities for the (001) and (002) peaks confirms the C 2/ m symmetry of all Fe 1– x Ni x PS 3 crystals . The extracted values of the peak position and its full-width at half-maximum (fwhm) for the (002) peak are shown in the same figure, which allows the accurate calculation of the distances between vdW layers of Fe 1– x Ni x PS 3 .…”

“…The properties of MPX 3 materials can be tuned in different ways using intercalation between layers or adsorption of different species on top. ,− Here, MPX 3 , for example, can be converted from the antiferromagnetic into ferromagnetic state, and such systems might find broad applications in different areas. Also the mutual substitution of S and Se allows making a fine-tuning of the band gap in the MPX 3 materials; however, the attempts to prepare the ordered Janus compounds failed due to the large dipole moment appearing in the single MPX 3 layers as a result of the imbalance of charge distribution between S and Se …”

Electronic Correlations in FexNiyPS3 Van der Waals Materials: Insights from Angle-Resolved Photoelectron Spectroscopy and DFT

“…12,18,20 Studied crystals have dimensions of, at least, 5 × 5 mm 2 and the crystallographic planes have an angle of 60°or 120°for the neighboring steps confirming the hexagonal symmetry of the studied crystals. As can be deduced from the XRD results, the symmetry of Fe x Ni y PS 3 corresponds to the C2/m space group 27 and the gradual replacement of Fe with Ni in MPX 3 leads to the decrease of the c′ = c/3 lattice constant (Figure 1a) from c′ = 6.5246 Å to c′ = 6.2908 Å, respectively.…”

Tailoring spin waves in 2D transition metal phosphorus trichalcogenides via atomic-layer substitution

“…Note: During the final stage of the review process, we became aware of the work of Jin et al 73 on the preparation of bulk FePS1.5Se1.5 from FePS3. This proves the feasibility of the preparation of the proposed Janus materials, since they belong to the same chemical family.…”