Five coordinated Mn in Ba4Mn2Si2Te9: synthesis, crystal structure, physical properties, and electronic structure

Yadav, Sweta and Jana, Subhendu and Panigrahi, Gopabandhu and Malladi, Sairam K. and Niranjan, Manish K. and Prakash, Jai (2022) Five coordinated Mn in Ba4Mn2Si2Te9: synthesis, crystal structure, physical properties, and electronic structure. Dalton Transactions, 51 (24). pp. 9265-9277. ISSN 1477-9226

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Abstract

We report the synthesis of single-crystals of a new transition metal-containing quaternary chalcogenide, Ba4Mn2Si2Te9, synthesized by the solid-state method at 1273 K. A single-crystal X-ray diffraction study shows that it crystallizes in the orthorhombic crystal system (space group: Pbam) with cell constants of a = 13.4690(6) Å, b = 8.7223(4) Å, and c = 10.0032(4) Å. The asymmetric unit of the structure consists of eight unique crystallographic sites: one Ba, two Mn, one Si, and four Te sites. In this structure, the two Mn sites, Mn(1) and Mn(2), are disordered, each with fractional occupancy of 50%. The short distance of 2.170(3) Å between Mn(1) and Mn(2) implies that both Mn sites are not occupied simultaneously. The Mn atoms show two types of polyhedra: unique Mn(1)Te5 units along with traditional Mn(2)Te4 tetrahedra. The main motifs of the Ba4Mn2Si2Te9 structure are dimeric Si2Te6 units (with Si-Si single bond), Mn(1)Te5, and Mn(2)Te4 polyhedra. The structure can be described as pseudo-two-dimensional if only Mn(1) atoms are present and one-dimensional when only Mn(2) atoms are filled in the structure. The extended 2∞[Mn(1)Si2Te9]10− layers and 1∞[Mn(2)Si2Te8]8− chains are separated by Ba2+ cations. The direct bandgap for the polycrystalline Ba4Mn2Si2Te9 sample is 0.6(1) eV, as determined from an optical absorption study consistent with the sample's black color. The resistivity study of the polycrystalline Ba4Mn2Si2Te9 also confirms the semiconducting behavior. The thermal conductivity (κ) values are extremely low and decrease with increasing temperature up to 0.46 W m−1 K−1 at 773 K. The DFT studies suggest that the computed bandgap depends on the magnetic ordering of Mn magnetic moments, and the value varies from ∼0.3-1.0 eV. Relative inter-atomic bond strengths of pertinent atom pairs have been analyzed using the crystal orbital Hamilton populations (COHP). © 2022 The Royal Society of Chemistry.

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IITH Creators:

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

Item Type:

Article

Additional Information:

JP thanks DST-SERB, the Government of India (GOI) for the financial support under the Core Research (CRG) grant (Grant Number: CRG/2021/003641) and ECR grant (ECR/2017/000822), and IIT Hyderabad for Seed Grant and Research facilities. SY thanks the Ministry of Education (MOE), GOI for Prime Minister's Research Fellowship (PMRF). SJ and GP thank MOE, GOI India, and IIT Hyderabad for the research fellowships. The authors also gratefully acknowledge DST-FIST (SR/FST/ETI-421/2016) for the SEM-EDAX facility and DST-FIST (SR/FST/PSI-215/2016) for computational resources used in this work.

Uncontrolled Keywords:

Crystals structures; Electronic.structure; Five-coordinated; Orthorhombic crystal system; Physical electronics; Polycrystalline; Quaternary chalcogenides; Single-crystal X-ray diffraction studies; Solid state method; Synthesised

Subjects:

Physics
Chemistry
Materials Engineering > Materials engineering

Divisions:

Department of Chemistry
Department of Material Science Engineering
Department of Physics

Depositing User:

. LibTrainee 2021

Date Deposited:

13 Oct 2022 13:40

Last Modified:

13 Oct 2022 13:41

URI:

http://raiithold.iith.ac.in/id/eprint/10925