Chalcogen dependent metal vacancies and disorder in Ba2Ln1−Mn2−S5 and Ba2−Ln1−Mn2−Se5 (Ln = Pr, Nd, and Gd) structures

Malladi, Sairam K and Niranjan, Manish K and Prakash, J. and et al, . (2022) Chalcogen dependent metal vacancies and disorder in Ba2Ln1−Mn2−S5 and Ba2−Ln1−Mn2−Se5 (Ln = Pr, Nd, and Gd) structures. Journal of Alloys and Compounds, 901. pp. 1-12. ISSN 0925-8388

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Abstract

Single crystals of six new non-stoichiometric quaternary chalcogenides with a general formula Ba2−δLn1−xMn2−yQ5 (Ln = Pr, Nd, and Gd; Q = S and Se) have been synthesized by the molten flux method. Single crystal X-ray diffraction (SCXRD) studies show that these compounds are isostructural and crystallize in the monoclinic space group C2/m with two formula units. These structures show occupational disorder at the metal sites, and the SCXRD refined compositions of these compounds are Ba2Pr0.88(1)Mn1.79(1)S5, Ba2Nd0.83(1)Mn1.89(1)S5, Ba2Gd0.82(1)Mn1.77(1)S5, Ba1.86(1)Pr0.61(1)Mn1.88(1)Se5, Ba1.90(1)Nd0.57(1)Mn1.93(1)Se5, and Ba1.88(1)Gd0.56(1)Mn1.95(1)Se5. The sulfide structures have split positions for Mn atoms with the concomitant occupational disorder at the Pr and Mn sites. In contrast, the selenide structures do not exhibit split Mn sites. The Ba sites in these selenides also show occupational disorder along with partially occupied Ln and Mn sites. The crystal structures of the selenides are comprised of [2∞Ln1−xMn2−ySe5]n− layers separated by Ba2+ cations. The Ln atoms in these sulfides and selenides are octahedrally coordinated with six Q atoms, and each Mn atom is bonded with four Q atoms forming a distorted tetrahedral geometry. The charge balancing in these structures is difficult due to the metal vacancies. The optical absorption study on the polycrystalline Ba1.88Gd0.56Mn1.95Se5 sample reveals a direct bandgap of 1.73(2) eV in agreement with the reddish color of the sample. The density functional calculations are performed to study the atomic and electronic structures of Ba1.88(1)Gd0.56(1)Mn1.95(1)Se5. © 2022 Elsevier B.V.

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IITH Creators:

IITH Creators	ORCiD
Malladi, Sairam K	https://orcid.org/0000-0002-0322-8137
Niranjan, Manish K	https://orcid.org/0000-0002-4417-5107
Prakash, J.	https://orcid.org/0000-0002-4078-9662

Item Type:

Article

Additional Information:

JP thanks DST-SERB, Government of India for the financial support under the early career research (ECR) award (Grant number: ECR/2017/000822 ), and IIT Hyderabad for seed grant and research facilities. GP and SJ thank MoE, IIT Hyderabad for the research fellowships. MI thanks DST-SERB, Government of India (Grant number: ECR/2017/000822) for the research fellowship. The authors also gratefully acknowledge DST-FIST ( SR/FST/ETI-421/2016 ) for the SEM-EDS facility and DST-FIST ( SR/FST/PSI-215/2016 ) for computational resources used in this work.

Uncontrolled Keywords:

Crystal structure; DFT study; Metal chalcogenides; Single crystal X-ray diffraction; Solid-state synthesis

Subjects:

Others > Metallurgy Metallurgical Engineering
Physics
Chemistry
Materials Engineering > Materials engineering

Divisions:

Department of Chemistry
Department of Material Science Engineering
Department of Physics

Depositing User:

. LibTrainee 2021

Date Deposited:

30 Jun 2022 11:14

Last Modified:

27 Jul 2022 05:52