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At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Te4MoW3(SeS)2 by Materials Project

WTe2MoTe2WSe2WS2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one MoTe2 sheet oriented in the (0, 0, 1) direction; one WS2 sheet oriented in the (0, 0, 1) direction; one WSe2 sheet oriented in the (0, 0, 1) direction; and one WTe2 sheet oriented in the (0, 0, 1) direction. In the MoTe2 sheet, Mo6+ is bonded to six Te2- atoms to form distorted edge-sharing MoTe6 pentagonal pyramids. All Mo–Te bond lengths are 2.71 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent Mo6+ atoms. In the second Te2- site, Te2- is bonded in a 12-coordinate geometry to three equivalent Mo6+ atoms. In the WS2 sheet, W+3.33+ is bonded to six S2- atoms to form distorted edge-sharing WS6 pentagonal pyramids. All W–S bond lengths are 2.47 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent W+3.33+ atoms. In the second S2- site, S2- is bonded in a 3-coordinate geometry to three equivalent W+3.33+ atoms. In the WSe2 sheet, W+3.33+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing WSe6 pentagonal pyramids. All W–Se bond lengths are 2.57 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent W+3.33+ atoms. In the WTe2 sheet, W+3.33+ is bonded to six Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.72 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 12-coordinate geometry to three equivalent W+3.33+ atoms. In the second Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent W+3.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PW3 by Materials Project

W3P crystallizes in the tetragonal I-42m space group. The structure is three-dimensional. there are three inequivalent W sites. In the first W site, W is bonded in a 2-coordinate geometry to two equivalent P atoms. Both W–P bond lengths are 2.53 Å. In the second W site, W is bonded in a distorted bent 120 degrees geometry to two equivalent P atoms. Both W–P bond lengths are 2.44 Å. In the third W site, W is bonded in a 4-coordinate geometry to four equivalent P atoms. All W–P bond lengths are 2.51 Å. P is bonded in a 8-coordinate geometry to eight W atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K(WO3)3 by Materials Project

K(WO3)3 crystallizes in the orthorhombic Cmm2 space group. The structure is three-dimensional. K1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are two shorter (3.11 Å) and four longer (3.15 Å) K–O bond lengths. There are two inequivalent W+5.67+ sites. In the first W+5.67+ site, W+5.67+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 0–31°. There is two shorter (1.94 Å) and four longer (1.95 Å) W–O bond length. In the second W+5.67+ site, W+5.67+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 0–33°. There are a spread of W–O bond distances ranging from 1.94–1.96 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two W+5.67+ atoms. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two equivalent W+5.67+ atoms. In the third O2- site, O2- is bonded in a linear geometry to two equivalent W+5.67+ atoms. In the fourth O2- site, O2- is bonded in a linear geometry to two equivalent W+5.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on W4C3O by Materials Project

W4C3O is Tungsten Carbide-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. there are two inequivalent W+3.50+ sites. In the first W+3.50+ site, W+3.50+ is bonded to three equivalent C4- and three equivalent O2- atoms to form a mixture of distorted edge, face, and corner-sharing WC3O3 pentagonal pyramids. All W–C bond lengths are 2.19 Å. All W–O bond lengths are 2.38 Å. In the second W+3.50+ site, W+3.50+ is bonded to six C4- atoms to form distorted WC6 pentagonal pyramids that share corners with twelve WC3O3 pentagonal pyramids, edges with six equivalent WC6 pentagonal pyramids, and faces with two WC3O3 pentagonal pyramids. There are three shorter (2.23 Å) and three longer (2.25 Å) W–C bond lengths. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded to six W+3.50+ atoms to form a mixture of distorted edge, face, and corner-sharing CW6 pentagonal pyramids. In the second C4- site, C4- is bonded to six equivalent W+3.50+ atoms to form a mixture of distorted edge, face, and corner-sharing CW6 pentagonal pyramids. O2- is bonded in a 6-coordinate geometry to six equivalent W+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PW3 by Materials Project

W3P crystallizes in the tetragonal I-4 space group. The structure is three-dimensional. there are three inequivalent W sites. In the first W site, W is bonded in a 2-coordinate geometry to two equivalent P atoms. There are one shorter (2.53 Å) and one longer (2.54 Å) W–P bond lengths. In the second W site, W is bonded in a 4-coordinate geometry to four equivalent P atoms. There are a spread of W–P bond distances ranging from 2.50–2.53 Å. In the third W site, W is bonded in a distorted bent 120 degrees geometry to two equivalent P atoms. There are one shorter (2.44 Å) and one longer (2.46 Å) W–P bond lengths. P is bonded in a 8-coordinate geometry to eight W atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VW3 by Materials Project

VW3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. V is bonded in a distorted body-centered cubic geometry to fourteen W atoms. There are eight shorter (2.72 Å) and six longer (3.14 Å) V–W bond lengths. There are two inequivalent W sites. In the first W site, W is bonded to four equivalent V and four equivalent W atoms to form a mixture of distorted edge, face, and corner-sharing WV4W4 tetrahedra. All W–W bond lengths are 2.72 Å. In the second W site, W is bonded in a 8-coordinate geometry to six equivalent V and eight equivalent W atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Factors controlling marine aerosol size distributions and their climate effects over the northwest Atlantic Ocean region

Abstract. Aerosols over Earth's remote and spatially extensive ocean surfaces have important influences on planetary climate. However, these aerosols and their effects remain poorly understood, in part due to the remoteness and limited observations over these regions. In this study, we seek to understand factors that shape marine aerosol size distributions and composition in the northwest Atlantic Ocean region. We use the GEOS-Chem model with the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm model to interpret measurements collected from ship and aircraft during the four seasonal campaigns of the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) conducted between 2015 and 2018. Observations from the NAAMES campaigns show enhancements in the campaign-median number of aerosols with diameters larger than 3 nm in the lower troposphere (below 6 km), most pronounced during the phytoplankton bloom maxima (May/June) below 2 km in the free troposphere. Our simulations, combined with NAAMES ship and aircraft measurements, suggest several key factors that contribute to aerosol number and size in the northwest Atlantic lower troposphere, with significant regional-mean (40–60∘ N and 20–50∘ W) cloud-albedo aerosol indirect effect (AIE) and direct radiative effect (DRE) processes during the phytoplankton bloom. These key factors and their associated simulated radiative effects in the region include the following: (1) particle formation near and above the marine boundary layer (MBL) top (AIE: −3.37 W m−2, DRE: −0.62 W m−2); (2) particle growth due to marine secondary organic aerosol (MSOA) as the nascent particles subside into the MBL, enabling them to become cloud-condensation-nuclei-sized particles (AIE: −2.27 W m−2, DRE: −0.10 W m−2); (3) particle formation and growth due to the products of dimethyl sulfide, above and within the MBL (−1.29 W m−2, DRE: −0.06 W m−2); (4) ship emissions (AIE: −0.62 W m−2, DRE: −0.05 W m−2); and (5) primary sea spray emissions (AIE: +0.04 W m−2, DRE: −0.79 W m−2). Our results suggest that a synergy of particle formation in the lower troposphere (particularly near and above the MBL top) and growth by MSOA contributes strongly to cloud-condensation-nuclei-sized particles with significant regional radiative effects in the northwest Atlantic. To gain confidence in radiative effect magnitudes, future work is needed to understand (1) the sources and temperature dependence of condensable marine vapors forming MSOA, (2) primary sea spray emissions, and (3) the species that can form new particles in the lower troposphere and grow these particles as they descend into the marine boundary layer.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1979

The condition of a finite Markov chain and perturbation bounds for the limiting probabilities

The inequalities bounding the relative error the norm of w- w squiggly/the norm of w are exhibited by a very simple function of E and A. Let T denote the transition matrix of an ergodic chain, C, and let A = I - T. Let E be a perturbation matrix such that T squiggly = T - E is also the transition matrix of an ergodic chain, C squiggly. Let w and w squiggly denote the limiting probability (row) vectors for C and C squiggly. The inequality is the best one possible. This bound can be significant in the numerical determination of the limiting probabilities for an ergodic chain. In addition to presenting a sharp bound for the norm of w-w squiggly/the norm of w an explicit expression for w squiggly will be derived in which w squiggly is given as a function of E, A, w and some other related terms.

Meyer, C. D., Jr.↗
NASA NTRS1980

Remote sensing of soil moisture content over bare fields at 1.4 GHz frequency

A simple method of estimating moisture content (W) of a bare soil from the observed brightness temperature (T sub B) at 1.4 GHz is discussed. The method is based on a radiative transfer model calculation, which has been successfully used in the past to account for many observational results, with some modifications to take into account the effect of surface roughness. Besides the measured T sub B's, the three additional inputs required by the method are the effective soil thermodynamic temperature, the precise relation between W and the smooth field brightness temperature T sub B and a parameter specifying the surface roughness characteristics. The soil effective temperature can be readily measured and the procedures of estimating surface roughness parameter and obtaining the relation between W and smooth field brightness temperature are discussed in detail. Dual polarized radiometric measurements at an off-nadir incident angle are sufficient to estimate both surface roughness parameter and W, provided that the relation between W and smooth field brightness temperature at the same angle is known. The method of W estimate is demonstrated with two sets of experimental data, one from a controlled field experiment by a mobile tower and the other, from aircraft overflight. The results from both data sets are encouraging when the estimated W's are compared with the acquired ground truth of W's in the top 2 cm layer. An offset between the estimated and the measured W's exists in the results of the analyses, but that can be accounted for by the presently poor knowledge of the relationship between W and smooth field brightness temperature for various types of soils. An approach to quantify this relationship for different soils and thus improve the method of W estimate is suggested.

Wang, J. R.↗
DOE OSTI2020

Materials Data on As3W2 by Materials Project

W2As3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent W+4.50+ sites. In the first W+4.50+ site, W+4.50+ is bonded to six As3- atoms to form a mixture of distorted face, edge, and corner-sharing WAs6 octahedra. The corner-sharing octahedra tilt angles range from 44–55°. There are a spread of W–As bond distances ranging from 2.55–2.63 Å. In the second W+4.50+ site, W+4.50+ is bonded to six As3- atoms to form a mixture of face, edge, and corner-sharing WAs6 octahedra. The corner-sharing octahedra tilt angles range from 44–55°. There are a spread of W–As bond distances ranging from 2.55–2.60 Å. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded in a 5-coordinate geometry to four W+4.50+ and one As3- atom. The As–As bond length is 2.52 Å. In the second As3- site, As3- is bonded in a 4-coordinate geometry to four W+4.50+ atoms. In the third As3- site, As3- is bonded in a 5-coordinate geometry to four W+4.50+ and one As3- atom. The As–As bond length is 2.95 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NiP3W2 by Materials Project

W2NiP3 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent W+3.50+ sites. In the first W+3.50+ site, W+3.50+ is bonded to six P3- atoms to form distorted WP6 octahedra that share corners with four equivalent NiP6 octahedra, corners with eight equivalent WP6 octahedra, edges with two equivalent NiP6 octahedra, edges with four equivalent WP6 octahedra, a faceface with one WP6 octahedra, and a faceface with one NiP6 octahedra. The corner-sharing octahedra tilt angles range from 41–54°. There are a spread of W–P bond distances ranging from 2.45–2.54 Å. In the second W+3.50+ site, W+3.50+ is bonded to six P3- atoms to form WP6 octahedra that share corners with four equivalent NiP6 octahedra, corners with eight equivalent WP6 octahedra, edges with two equivalent NiP6 octahedra, edges with four equivalent WP6 octahedra, a faceface with one WP6 octahedra, and a faceface with one NiP6 octahedra. The corner-sharing octahedra tilt angles range from 41–59°. There are a spread of W–P bond distances ranging from 2.44–2.53 Å. There are two inequivalent Ni2+ sites. In the first Ni2+ site, Ni2+ is bonded to six P3- atoms to form NiP6 octahedra that share corners with four equivalent NiP6 octahedra, corners with eight equivalent WP6 octahedra, edges with two equivalent NiP6 octahedra, edges with four equivalent WP6 octahedra, and faces with two equivalent WP6 octahedra. The corner-sharing octahedra tilt angles range from 45–54°. There are four shorter (2.25 Å) and two longer (2.57 Å) Ni–P bond lengths. In the second Ni2+ site, Ni2+ is bonded to six P3- atoms to form NiP6 octahedra that share corners with four equivalent NiP6 octahedra, corners with eight equivalent WP6 octahedra, edges with two equivalent NiP6 octahedra, edges with four equivalent WP6 octahedra, and faces with two equivalent WP6 octahedra. The corner-sharing octahedra tilt angles range from 45–59°. There are two shorter (2.33 Å) and four longer (2.37 Å) Ni–P bond lengths. There are three inequivalent P3- sites. In the first P3- site, P3- is bonded in a 6-coordinate geometry to four W+3.50+ and two equivalent Ni2+ atoms. In the second P3- site, P3- is bonded in a 6-coordinate geometry to five W+3.50+ and one Ni2+ atom. In the third P3- site, P3- is bonded in a 6-coordinate geometry to three W+3.50+ and three Ni2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al5W by Materials Project

Al5W crystallizes in the hexagonal P6_322 space group. The structure is three-dimensional. there are two inequivalent W sites. In the first W site, W is bonded to twelve Al atoms to form WAl12 cuboctahedra that share corners with six equivalent WAl12 cuboctahedra, corners with twelve AlAl9W3 cuboctahedra, edges with six equivalent WAl12 cuboctahedra, and faces with eight AlAl9W3 cuboctahedra. There are six shorter (2.75 Å) and six longer (2.84 Å) W–Al bond lengths. In the second W site, W is bonded to twelve Al atoms to form WAl12 cuboctahedra that share corners with six equivalent WAl12 cuboctahedra, corners with twelve AlAl9W3 cuboctahedra, edges with six equivalent WAl12 cuboctahedra, and faces with eight AlAl9W3 cuboctahedra. There are six shorter (2.75 Å) and six longer (2.84 Å) W–Al bond lengths. There are three inequivalent Al sites. In the first Al site, Al is bonded to three equivalent W and nine Al atoms to form distorted AlAl9W3 cuboctahedra that share corners with nine WAl12 cuboctahedra, corners with nine equivalent AlAl9W3 cuboctahedra, edges with six equivalent AlAl9W3 cuboctahedra, faces with three equivalent WAl12 cuboctahedra, and faces with five AlAl9W3 cuboctahedra. There are six shorter (2.77 Å) and three longer (2.84 Å) Al–Al bond lengths. In the second Al site, Al is bonded to three equivalent W and nine Al atoms to form distorted AlAl9W3 cuboctahedra that share corners with three equivalent WAl12 cuboctahedra, corners with fifteen AlAl9W3 cuboctahedra, edges with six equivalent AlAl9W3 cuboctahedra, faces with three equivalent AlAl9W3 cuboctahedra, and faces with five WAl12 cuboctahedra. All Al–Al bond lengths are 2.75 Å. In the third Al site, Al is bonded in a distorted bent 150 degrees geometry to two W and four Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co2W4C by Materials Project

Co2W4C crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are two inequivalent W sites. In the first W site, W is bonded in a 2-coordinate geometry to four equivalent Co and two equivalent C atoms. There are two shorter (2.71 Å) and two longer (2.92 Å) W–Co bond lengths. Both W–C bond lengths are 2.13 Å. In the second W site, W is bonded in a distorted hexagonal planar geometry to six equivalent Co atoms. All W–Co bond lengths are 2.44 Å. Co is bonded in a 12-coordinate geometry to nine W and three equivalent Co atoms. All Co–Co bond lengths are 2.61 Å. C is bonded to six equivalent W atoms to form corner-sharing CW6 octahedra. The corner-sharing octahedral tilt angles are 39°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni2W4C by Materials Project

Ni2W4C crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are two inequivalent W sites. In the first W site, W is bonded in a 2-coordinate geometry to four equivalent Ni and two equivalent C atoms. There are two shorter (2.68 Å) and two longer (2.88 Å) W–Ni bond lengths. Both W–C bond lengths are 2.14 Å. In the second W site, W is bonded in a 6-coordinate geometry to six equivalent Ni atoms. All W–Ni bond lengths are 2.45 Å. Ni is bonded in a 12-coordinate geometry to nine W and three equivalent Ni atoms. All Ni–Ni bond lengths are 2.67 Å. C is bonded to six equivalent W atoms to form corner-sharing CW6 octahedra. The corner-sharing octahedral tilt angles are 41°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on W3O8 by Materials Project

W3O8 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two W3O8 sheets oriented in the (1, 0, 0) direction. there are two inequivalent W+5.33+ sites. In the first W+5.33+ site, W+5.33+ is bonded to six O2- atoms to form edge-sharing WO6 octahedra. All W–O bond lengths are 1.96 Å. In the second W+5.33+ site, W+5.33+ is bonded to six O2- atoms to form distorted edge-sharing WO6 octahedra. There are a spread of W–O bond distances ranging from 1.95–2.22 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in an L-shaped geometry to two equivalent W+5.33+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to three W+5.33+ atoms. In the third O2- site, O2- is bonded in a water-like geometry to two W+5.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te2MoW3(SeS2)2 by Materials Project

WTe2WSe2WS2MoS2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one MoS2 sheet oriented in the (0, 0, 1) direction; one WS2 sheet oriented in the (0, 0, 1) direction; one WSe2 sheet oriented in the (0, 0, 1) direction; and one WTe2 sheet oriented in the (0, 0, 1) direction. In the MoS2 sheet, Mo6+ is bonded to six S2- atoms to form distorted edge-sharing MoS6 pentagonal pyramids. All Mo–S bond lengths are 2.45 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent Mo6+ atoms. In the second S2- site, S2- is bonded in a 3-coordinate geometry to three equivalent Mo6+ atoms. In the WS2 sheet, W+3.33+ is bonded to six equivalent S2- atoms to form distorted edge-sharing WS6 pentagonal pyramids. All W–S bond lengths are 2.45 Å. S2- is bonded in a 3-coordinate geometry to three equivalent W+3.33+ atoms. In the WSe2 sheet, W+3.33+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing WSe6 pentagonal pyramids. All W–Se bond lengths are 2.55 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent W+3.33+ atoms. In the WTe2 sheet, W+3.33+ is bonded to six Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.71 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent W+3.33+ atoms. In the second Te2- site, Te2- is bonded in a 12-coordinate geometry to three equivalent W+3.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te4MoW3(SeS)2 by Materials Project

WTe2MoTe2WSe2WS2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one MoTe2 sheet oriented in the (0, 0, 1) direction; one WS2 sheet oriented in the (0, 0, 1) direction; one WSe2 sheet oriented in the (0, 0, 1) direction; and one WTe2 sheet oriented in the (0, 0, 1) direction. In the MoTe2 sheet, Mo6+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing MoTe6 pentagonal pyramids. All Mo–Te bond lengths are 2.71 Å. Te2- is bonded in a 12-coordinate geometry to three equivalent Mo6+ atoms. In the WS2 sheet, W+3.33+ is bonded to six equivalent S2- atoms to form distorted edge-sharing WS6 pentagonal pyramids. All W–S bond lengths are 2.47 Å. S2- is bonded in a 3-coordinate geometry to three equivalent W+3.33+ atoms. In the WSe2 sheet, W+3.33+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing WSe6 pentagonal pyramids. All W–Se bond lengths are 2.57 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent W+3.33+ atoms. In the WTe2 sheet, W+3.33+ is bonded to six Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.72 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent W+3.33+ atoms. In the second Te2- site, Te2- is bonded in a 12-coordinate geometry to three equivalent W+3.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te2MoW3(Se2S)2 by Materials Project

WTe2WSe2MoSe2WS2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one MoSe2 sheet oriented in the (0, 0, 1) direction; one WS2 sheet oriented in the (0, 0, 1) direction; one WSe2 sheet oriented in the (0, 0, 1) direction; and one WTe2 sheet oriented in the (0, 0, 1) direction. In the MoSe2 sheet, Mo6+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing MoSe6 pentagonal pyramids. All Mo–Se bond lengths are 2.55 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Mo6+ atoms. In the WS2 sheet, W+3.33+ is bonded to six S2- atoms to form distorted edge-sharing WS6 pentagonal pyramids. All W–S bond lengths are 2.46 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 3-coordinate geometry to three equivalent W+3.33+ atoms. In the second S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent W+3.33+ atoms. In the WSe2 sheet, W+3.33+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing WSe6 pentagonal pyramids. All W–Se bond lengths are 2.56 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent W+3.33+ atoms. In the WTe2 sheet, W+3.33+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.71 Å. Te2- is bonded in a 12-coordinate geometry to three equivalent W+3.33+ atoms.

36 MATERIALS SCIENCE↗