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DOE OSTI2024

Tree foliage as a net accumulator of highly toxic methylmercury

Tree canopies are known to elevate atmospheric inputs of both mercury (Hg) and methylmercury (MeHg). While foliar uptake of gaseous Hg is well documented, little is known regarding the temporal dynamics and origins of MeHg in tree foliage, which represents typically less than 1% of total Hg in foliage. In this work, we examined the foliar total Hg and MeHg content by following the growth of five individual trees of American Beech (Fagus grandifolia) for one growing season (April–November, 2017) in North Carolina, USA. We show that similar to other studies foliar Hg content increased almost linearly over time, with daily accumulation rates ranging from 0.123 to 0.161 ng/g/day. However, not all trees showed linear increases of foliar MeHg content along the growing season; we found that 2 out of 5 trees showed elevated foliar MeHg content at the initial phase of the growing season but their MeHg content declined through early summer. However, foliar MeHg content among all 5 trees showed eventual increases through the end of the growing season, proving that foliage is a net accumulator of MeHg while foliar gain of biomass did not “dilute” MeHg content.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2023

How does Mercury Methylation Respond to Intensive Forest Management and the Creation of Anoxia in Floodplain Soils

This research endeavor, entitled “How does Mercury Methylation Respond to Intensive Forest Management and the Creation of Anoxia in Floodplain Soils?” represents a collaborative effort undertaken by the University of North Carolina at Greensboro, led by Principal Investigator Dr. James S. Coleman, the United States Forest Service Santee Experimental Forest (SEF) Station Director Dr. Carl C. Trettin as Co-Principal Investigator, and The Chinese University of Hong Kong Dr. Martin Tsz-Ki Tsui and Dr. Alex T. Chow serving as Co-Principal Investigators. The overarching objective of this proposed project was to capture and elucidate the immediate and short-term effects of forest disturbances, namely clear-cutting and thinning, on the biogeochemical cycling of mercury (Hg) within the SEF in Huger, South Carolina. To accomplish this objective, a two-year exploratory study was proposed to conduct soil sampling and measurements of Hg and toxic methylmercury (MeHg), and soil physiochemical data within the experimental watershed (WS77) at SEF, following the clear-cutting process initiated for the preparation of the native longleaf pine restoration project by the USFS. Based on our mercury and hydrological data assessment, we concluded that the implementation of forest management practices, particularly mechanical thinning and clear-cutting, appears to enhance the potential for Hg methylation. Furthermore, these forest management practices may disrupt and alter the storage, mobility, and transformations of atmospherically deposited Hg in these lowland forests. We advocate for further research to comprehensively evaluate the impact of forest management on Hg cycling within forest ecosystems.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2024

Mercury trophic transfer in Bear Creek

Mercury (especially when transformed by environmental microbes into methylmercury [MeHg]) is one of the only metals known to biomagnify in aquatic food webs, leading to elevated concentrations of this toxicant in fish. However, because Hg is predominantly accumulated in fish via dietary rather than aqueous exposure, the link between aqueous Hg concentrations and concentrations in fish is not always straightforward. This is particularly confounding for remediation efforts at contaminated sites because although reducing aqueous Hg concentrations may be achievable, concentrations in fish may not respond to these reductions in aqueous concentrations if a sufficient amount of Hg remains within the food web or if conditions favor Hg methylation in the environment.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2024

Mercury Trophic Transfer in Bear Creek

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2022

Genome-Wide Association Study Reveals Complex Genetic Architecture of Cadmium and Mercury Accumulation and Tolerance Traits in Medicago truncatula

Heavy metals are an increasing problem due to contamination from human sources that and can enter the food chain by being taken up by plants. Understanding the genetic basis of accumulation and tolerance in plants is important for reducing the uptake of toxic metals in crops and crop relatives, as well as for removing heavy metals from soils by means of phytoremediation. Following exposure of Medicago truncatula seedlings to cadmium (Cd) and mercury (Hg), we conducted a genome-wide association study using relative root growth (RRG) and leaf accumulation measurements. Cd and Hg accumulation and RRG had heritability ranging 0.44 – 0.72 indicating high genetic diversity for these traits. The Cd and Hg trait associations were broadly distributed throughout the genome, indicated the traits are polygenic and involve several quantitative loci. For all traits, candidate genes included several membrane associated ATP-binding cassette transporters, P-type ATPase transporters, oxidative stress response genes, and stress related UDP-glycosyltransferases. The P-type ATPase transporters and ATP-binding cassette protein-families have roles in vacuole transport of heavy metals, and our findings support their wide use in physiological plant responses to heavy metals and abiotic stresses. We also found associations between Cd RRG with the genes CAX3 and PDR3, two linked adjacent genes, and leaf accumulation of Hg associated with the genes NRAMP6 and CAX9. When plant genotypes with the most extreme phenotypes were compared, we found significant divergence in genomic regions using population genomics methods that contained metal transport and stress response gene ontologies. Several of these genomic regions show high linkage disequilibrium (LD) among candidate genes suggesting they have evolved together. Minor allele frequency (MAF) and effect size of the most significant SNPs was negatively correlated with large effect alleles being most rare. This is consistent with purifying selection against alleles that increase toxicity and abiotic stress. Conversely, the alleles with large affect that had higher frequencies that were associated with the exclusion of Cd and Hg. Overall, macroevolutionary conservation of heavy metal and stress response genes is important for improvement of forage crops by harnessing wild genetic variants in gene banks such as the Medicago HapMap collection.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2020

Mercury Speciation via Diffusive Gradients Thin-Films Technology

Objectives: Develop and test various diffusive gradient in thin films (DGT) samplers for mercury - SRNL is developing reactive DGTS (rDGTs). Test chemistry to differentiate methylmercury from total and/or inorganic mercury in environmental samples. Fabricate and test rDGT samplers for deployment. Deploy the rDGTs in variable settings. Mercury is a persistent-bioaccumulative-toxic environmental pollutant. Mercury exists in different species such as elemental, inorganic, and methyl. Mercury speciation determine mercury behavior and toxicity. For example, methylmercury strongly accumulates in biota such as fish resulting in potential human health impacts. DGTs are innovative samplers to measure water concentration by diffusion and capture. Types of Hg DGTs used: Total Hg, Inorganic Hg, and Methyl Hg. Deployment Sites: Upper Three Runs, Lower Three Runs, Steele Creek, East Fork Poplar Creek (SRNL Sites), Horizons Creek, NOA Creek, Bruners Creek (ORNL Sites). DGT concentration estimates closely matched alternative measurements for soluble mercury at each Oak Ridge site - DGTs did not respond to particulate mercury. DGTs provide a representative measure for biota uptake since they are left out longer which allows for an average exposure concentration. DMA-80 provided an efficient and quick analysis. Variability in site location made a difference in Hg species. DGT preparations and sampling wasn't as quick and simple as microcolumn technology. Copper reagent degraded agarose gel - more work and cleaner data are needed to assess speciation in rDGTs. Future Work: Use cross-linked polyacrylamide for the collection layer for a stronger plastic. Make a copper diffusion layer without agarose. Test copper separation in lab using realistic stream conditions such as high organic carbon.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

A consensus protocol for the recovery of mercury methylation genes from metagenomes

Abstract Mercury (Hg) methylation genes ( hgcAB ) mediate the formation of the toxic methylmercury and have been identified from diverse environments, including freshwater and marine ecosystems, Arctic permafrost, forest and paddy soils, coal‐ash amended sediments, chlor‐alkali plants discharges and geothermal springs. Here we present the first attempt at a standardized protocol for the detection, identification and quantification of hgc genes from metagenomes. Our Hg‐cycling microorganisms in aquatic and terrestrial ecosystems (Hg‐MATE) database, a catalogue of hgc genes, provides the most accurate information to date on the taxonomic identity and functional/metabolic attributes of microorganisms responsible for Hg methylation in the environment. Furthermore, we introduce “marky‐coco”, a ready‐to‐use bioinformatic pipeline based on de novo single‐metagenome assembly, for easy and accurate characterization of hgc genes from environmental samples. We compared the recovery of hgc genes from environmental metagenomes using the marky‐coco pipeline with an approach based on coassembly of multiple metagenomes. Our data show similar efficiency in both approaches for most environments except those with high diversity (i.e., paddy soils) for which a coassembly approach was preferred. Finally, we discuss the definition of true hgc genes and methods to normalize hgc gene counts from metagenomes.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2020

Materials Data on TlHg by Materials Project

Hg(Tl) is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Hg is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Hg–Tl bond lengths are 3.37 Å. Tl is bonded in a body-centered cubic geometry to eight equivalent Hg atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Si(Hg2S3)2 by Materials Project

Hg4SiS6 is Chalcostibite-like structured and crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are four inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a 5-coordinate geometry to five S2- atoms. There are a spread of Hg–S bond distances ranging from 2.58–3.30 Å. In the second Hg2+ site, Hg2+ is bonded to four S2- atoms to form HgS4 tetrahedra that share corners with two equivalent HgS4 tetrahedra and corners with two equivalent SiS4 tetrahedra. There are a spread of Hg–S bond distances ranging from 2.57–2.68 Å. In the third Hg2+ site, Hg2+ is bonded to four S2- atoms to form HgS4 tetrahedra that share corners with two equivalent HgS4 tetrahedra and corners with two equivalent SiS4 tetrahedra. There are a spread of Hg–S bond distances ranging from 2.56–2.74 Å. In the fourth Hg2+ site, Hg2+ is bonded in a 4-coordinate geometry to four S2- atoms. There are a spread of Hg–S bond distances ranging from 2.56–2.70 Å. Si4+ is bonded to four S2- atoms to form SiS4 tetrahedra that share corners with four HgS4 tetrahedra. There are a spread of Si–S bond distances ranging from 2.12–2.16 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded to four Hg2+ atoms to form corner-sharing SHg4 tetrahedra. In the second S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to two Hg2+ and one Si4+ atom. In the third S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to two Hg2+ and one Si4+ atom. In the fourth S2- site, S2- is bonded in a 3-coordinate geometry to three Hg2+ and one Si4+ atom. In the fifth S2- site, S2- is bonded to four Hg2+ atoms to form corner-sharing SHg4 tetrahedra. In the sixth S2- site, S2- is bonded in a 3-coordinate geometry to two Hg2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Si(Hg2Se3)2 by Materials Project

Hg4SiSe6 is Chalcostibite-like structured and crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are four inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a 5-coordinate geometry to five Se2- atoms. There are a spread of Hg–Se bond distances ranging from 2.71–3.49 Å. In the second Hg2+ site, Hg2+ is bonded to four Se2- atoms to form HgSe4 tetrahedra that share corners with two equivalent SiSe4 tetrahedra and corners with five HgSe4 tetrahedra. There are a spread of Hg–Se bond distances ranging from 2.66–2.83 Å. In the third Hg2+ site, Hg2+ is bonded to four Se2- atoms to form HgSe4 tetrahedra that share corners with two equivalent SiSe4 tetrahedra and corners with five HgSe4 tetrahedra. There are a spread of Hg–Se bond distances ranging from 2.69–2.85 Å. In the fourth Hg2+ site, Hg2+ is bonded to four Se2- atoms to form distorted HgSe4 tetrahedra that share corners with two equivalent SiSe4 tetrahedra and corners with six HgSe4 tetrahedra. There are a spread of Hg–Se bond distances ranging from 2.69–2.84 Å. Si4+ is bonded to four Se2- atoms to form SiSe4 tetrahedra that share corners with six HgSe4 tetrahedra. There are a spread of Si–Se bond distances ranging from 2.28–2.31 Å. There are six inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to four Hg2+ atoms to form distorted corner-sharing SeHg4 trigonal pyramids. In the second Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to two Hg2+ and one Si4+ atom. In the third Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to two Hg2+ and one Si4+ atom. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Hg2+ and one Si4+ atom. In the fifth Se2- site, Se2- is bonded to four Hg2+ atoms to form corner-sharing SeHg4 tetrahedra. In the sixth Se2- site, Se2- is bonded in a 3-coordinate geometry to two Hg2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Hg2Te2O7 by Materials Project

Hg2Te2O7 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are four inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a 4-coordinate geometry to four O2- atoms. There are two shorter (2.19 Å) and two longer (2.47 Å) Hg–O bond lengths. In the second Hg2+ site, Hg2+ is bonded in a 8-coordinate geometry to six O2- atoms. There are a spread of Hg–O bond distances ranging from 2.22–2.69 Å. In the third Hg2+ site, Hg2+ is bonded in a 2-coordinate geometry to four O2- atoms. There are two shorter (2.09 Å) and two longer (2.80 Å) Hg–O bond lengths. In the fourth Hg2+ site, Hg2+ is bonded to six O2- atoms to form distorted HgO6 pentagonal pyramids that share corners with four TeO6 octahedra. The corner-sharing octahedra tilt angles range from 50–56°. There are a spread of Hg–O bond distances ranging from 2.32–2.51 Å. There are three inequivalent Te5+ sites. In the first Te5+ site, Te5+ is bonded to six O2- atoms to form TeO6 octahedra that share corners with two equivalent TeO6 octahedra and corners with two equivalent HgO6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 37°. There is two shorter (1.95 Å) and four longer (1.98 Å) Te–O bond length. In the second Te5+ site, Te5+ is bonded to six O2- atoms to form TeO6 octahedra that share corners with two equivalent TeO6 octahedra and corners with two equivalent HgO6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 37°. There are a spread of Te–O bond distances ranging from 1.94–2.00 Å. In the third Te5+ site, Te5+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Te–O bond distances ranging from 1.93–2.17 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Te5+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Hg2+ and one Te5+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Hg2+ and two Te5+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Hg2+ and one Te5+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Hg2+ and two Te5+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Hg2+ and one Te5+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Hg2+ and one Te5+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on InHg by Materials Project

In(Hg) is Tungsten Carbide-like structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Hg is bonded in a 6-coordinate geometry to six equivalent In atoms. All Hg–In bond lengths are 3.13 Å. In is bonded in a 6-coordinate geometry to six equivalent Hg atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Hg3(ClO)2 by Materials Project

Hg3O2Cl2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a 6-coordinate geometry to three equivalent O2- and three equivalent Cl1- atoms. There are a spread of Hg–O bond distances ranging from 2.25–2.42 Å. There are a spread of Hg–Cl bond distances ranging from 2.71–3.26 Å. In the second Hg2+ site, Hg2+ is bonded in a distorted linear geometry to two equivalent O2- and four equivalent Cl1- atoms. Both Hg–O bond lengths are 2.11 Å. There are two shorter (3.07 Å) and two longer (3.08 Å) Hg–Cl bond lengths. O2- is bonded to four Hg2+ atoms to form a mixture of edge and corner-sharing OHg4 tetrahedra. Cl1- is bonded in a 5-coordinate geometry to five Hg2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CuHgSCl by Materials Project

CuHgSCl crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded to two equivalent S2- and two Cl1- atoms to form corner-sharing CuS2Cl2 tetrahedra. Both Cu–S bond lengths are 2.28 Å. There are one shorter (2.37 Å) and one longer (2.42 Å) Cu–Cl bond lengths. In the second Cu1+ site, Cu1+ is bonded in a trigonal planar geometry to two equivalent S2- and one Cl1- atom. Both Cu–S bond lengths are 2.25 Å. The Cu–Cl bond length is 2.28 Å. There are two inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a rectangular see-saw-like geometry to two S2- and two equivalent Cl1- atoms. There are one shorter (2.43 Å) and one longer (2.44 Å) Hg–S bond lengths. Both Hg–Cl bond lengths are 3.06 Å. In the second Hg2+ site, Hg2+ is bonded in a 4-coordinate geometry to two S2- and two equivalent Cl1- atoms. There are one shorter (2.43 Å) and one longer (2.44 Å) Hg–S bond lengths. Both Hg–Cl bond lengths are 3.04 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Cu1+ and two Hg2+ atoms to form SCu2Hg2 tetrahedra that share corners with two equivalent SCu2Hg2 tetrahedra, corners with four equivalent ClCu2Hg2 tetrahedra, and corners with two equivalent SCu2Hg2 trigonal pyramids. In the second S2- site, S2- is bonded to two equivalent Cu1+ and two Hg2+ atoms to form SCu2Hg2 trigonal pyramids that share corners with two equivalent SCu2Hg2 tetrahedra, corners with four equivalent ClCu2Hg2 tetrahedra, and corners with two equivalent SCu2Hg2 trigonal pyramids. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded to two Cu1+ and two equivalent Hg2+ atoms to form distorted ClCu2Hg2 tetrahedra that share corners with two equivalent ClCu2Hg2 tetrahedra, corners with four equivalent SCu2Hg2 tetrahedra, and corners with four equivalent SCu2Hg2 trigonal pyramids. In the second Cl1- site, Cl1- is bonded in a 1-coordinate geometry to one Cu1+ and two equivalent Hg2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on NbHg3F6 by Materials Project

(Hg)2NbHgF6 crystallizes in the trigonal P-31m space group. The structure is one-dimensional and consists of two mercury molecules and one NbHgF6 ribbon oriented in the (0, 0, 1) direction. In the NbHgF6 ribbon, Nb2+ is bonded to six equivalent F1- atoms to form NbF6 octahedra that share faces with two equivalent HgF6 cuboctahedra. All Nb–F bond lengths are 1.94 Å. Hg+1.33+ is bonded to six equivalent F1- atoms to form distorted HgF6 cuboctahedra that share faces with two equivalent NbF6 octahedra. All Hg–F bond lengths are 3.11 Å. F1- is bonded in a single-bond geometry to one Nb2+ and one Hg+1.33+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Hg4As2I3 by Materials Project

Hg4As2I3 crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. there are two inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a distorted rectangular see-saw-like geometry to one As+2.50- and three equivalent I1- atoms. The Hg–As bond length is 2.59 Å. All Hg–I bond lengths are 2.98 Å. In the second Hg2+ site, Hg2+ is bonded in a 6-coordinate geometry to two As+2.50- and four equivalent I1- atoms. There are one shorter (2.61 Å) and one longer (2.63 Å) Hg–As bond lengths. There are a spread of Hg–I bond distances ranging from 3.18–3.79 Å. There are two inequivalent As+2.50- sites. In the first As+2.50- site, As+2.50- is bonded to four Hg2+ atoms to form corner-sharing AsHg4 trigonal pyramids. In the second As+2.50- site, As+2.50- is bonded to three equivalent Hg2+ and one As+2.50- atom to form corner-sharing AsHg3As tetrahedra. The As–As bond length is 2.47 Å. I1- is bonded in a 2-coordinate geometry to five Hg2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Hg4Sb2I3 by Materials Project

Hg4Sb2I3 crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. there are two inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a distorted rectangular see-saw-like geometry to two Sb+2.50- and two equivalent I1- atoms. There are one shorter (2.77 Å) and one longer (2.78 Å) Hg–Sb bond lengths. There are one shorter (3.10 Å) and one longer (3.40 Å) Hg–I bond lengths. In the second Hg2+ site, Hg2+ is bonded in a distorted rectangular see-saw-like geometry to one Sb+2.50- and three equivalent I1- atoms. The Hg–Sb bond length is 2.75 Å. All Hg–I bond lengths are 3.03 Å. There are two inequivalent Sb+2.50- sites. In the first Sb+2.50- site, Sb+2.50- is bonded to four Hg2+ atoms to form corner-sharing SbHg4 trigonal pyramids. In the second Sb+2.50- site, Sb+2.50- is bonded to three equivalent Hg2+ and one Sb+2.50- atom to form corner-sharing SbHg3Sb tetrahedra. The Sb–Sb bond length is 2.84 Å. I1- is bonded in a trigonal non-coplanar geometry to three Hg2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Hg4As2Br3 by Materials Project

Hg4As2Br3 crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. there are two inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a distorted rectangular see-saw-like geometry to two As+2.50- and two equivalent Br1- atoms. There are one shorter (2.58 Å) and one longer (2.60 Å) Hg–As bond lengths. There are one shorter (2.99 Å) and one longer (3.19 Å) Hg–Br bond lengths. In the second Hg2+ site, Hg2+ is bonded in a distorted rectangular see-saw-like geometry to one As+2.50- and three equivalent Br1- atoms. The Hg–As bond length is 2.57 Å. All Hg–Br bond lengths are 2.84 Å. There are two inequivalent As+2.50- sites. In the first As+2.50- site, As+2.50- is bonded to three equivalent Hg2+ and one As+2.50- atom to form corner-sharing AsHg3As tetrahedra. The As–As bond length is 2.44 Å. In the second As+2.50- site, As+2.50- is bonded to four Hg2+ atoms to form corner-sharing AsHg4 trigonal pyramids. Br1- is bonded in a trigonal non-coplanar geometry to three Hg2+ atoms.

36 MATERIALS SCIENCE↗