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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Gd(SiPd)2 by Materials Project

Gd(PdSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 8-coordinate geometry to eight equivalent Pd and eight equivalent Si atoms. All Gd–Pd bond lengths are 3.26 Å. All Gd–Si bond lengths are 3.19 Å. Pd is bonded to four equivalent Gd and four equivalent Si atoms to form a mixture of distorted corner, edge, and face-sharing PdGd4Si4 tetrahedra. All Pd–Si bond lengths are 2.48 Å. Si is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Pd, and one Si atom. The Si–Si bond length is 2.34 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(SiIr)2 by Materials Project

Gd(IrSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 8-coordinate geometry to eight equivalent Ir and eight equivalent Si atoms. All Gd–Ir bond lengths are 3.24 Å. All Gd–Si bond lengths are 3.15 Å. Ir is bonded to four equivalent Gd and four equivalent Si atoms to form a mixture of distorted corner, edge, and face-sharing IrGd4Si4 tetrahedra. All Ir–Si bond lengths are 2.42 Å. Si is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Ir, and one Si atom. The Si–Si bond length is 2.46 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(GeRh)2 by Materials Project

Gd(RhGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent Ge atoms. All Gd–Rh bond lengths are 3.34 Å. All Gd–Ge bond lengths are 3.21 Å. Rh is bonded to four equivalent Gd and four equivalent Ge atoms to form a mixture of distorted edge, face, and corner-sharing RhGd4Ge4 tetrahedra. All Rh–Ge bond lengths are 2.47 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Rh, and one Ge atom. The Ge–Ge bond length is 2.56 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(PRu)2 by Materials Project

Gd(RuP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 8-coordinate geometry to eight equivalent Ru and eight equivalent P atoms. All Gd–Ru bond lengths are 3.16 Å. All Gd–P bond lengths are 3.13 Å. Ru is bonded in a 12-coordinate geometry to four equivalent Gd and four equivalent P atoms. All Ru–P bond lengths are 2.36 Å. P is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Ru, and one P atom. The P–P bond length is 2.45 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(BO2)6 by Materials Project

Gd(BO2)6 crystallizes in the trigonal R3c space group. The structure is three-dimensional. Gd is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Gd–O bond distances ranging from 2.35–2.55 Å. There are two inequivalent B sites. In the first B site, B is bonded in a tetrahedral geometry to four O atoms. There are a spread of B–O bond distances ranging from 1.44–1.51 Å. In the second B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.36–1.39 Å. There are four inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to one Gd and one B atom. In the second O site, O is bonded in a 2-coordinate geometry to one Gd and two B atoms. In the third O site, O is bonded in a distorted bent 120 degrees geometry to one Gd and two B atoms. In the fourth O site, O is bonded in a bent 120 degrees geometry to two B atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(BRu)2 by Materials Project

Gd(RuB)2 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Gd is bonded in a 10-coordinate geometry to four equivalent Ru and six equivalent B atoms. All Gd–Ru bond lengths are 3.00 Å. There are two shorter (2.82 Å) and four longer (3.02 Å) Gd–B bond lengths. Ru is bonded in a 4-coordinate geometry to two equivalent Gd and four equivalent B atoms. There are two shorter (2.07 Å) and two longer (2.16 Å) Ru–B bond lengths. B is bonded in a 7-coordinate geometry to three equivalent Gd and four equivalent Ru atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(Ge2Rh3)2 by Materials Project

Gd(Rh3Ge2)2 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Gd is bonded to six equivalent Rh and six equivalent Ge atoms to form face-sharing GdGe6Rh6 cuboctahedra. All Gd–Rh bond lengths are 3.16 Å. All Gd–Ge bond lengths are 3.13 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 5-coordinate geometry to five Ge atoms. There are one shorter (2.50 Å) and four longer (2.57 Å) Rh–Ge bond lengths. In the second Rh site, Rh is bonded in a 6-coordinate geometry to two equivalent Gd and four Ge atoms. There are two shorter (2.48 Å) and two longer (2.56 Å) Rh–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to nine Rh atoms. In the second Ge site, Ge is bonded in a 8-coordinate geometry to two equivalent Gd and six Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(Re2Si)2 by Materials Project

Gd(Re2Si)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Gd is bonded in a 6-coordinate geometry to twelve equivalent Re and six equivalent Si atoms. There are four shorter (3.25 Å) and eight longer (3.35 Å) Gd–Re bond lengths. There are four shorter (3.03 Å) and two longer (3.04 Å) Gd–Si bond lengths. Re is bonded to three equivalent Gd, six equivalent Re, and three equivalent Si atoms to form a mixture of distorted corner, edge, and face-sharing ReGd3Re6Si3 cuboctahedra. There are a spread of Re–Re bond distances ranging from 2.61–2.83 Å. There are one shorter (2.46 Å) and two longer (2.56 Å) Re–Si bond lengths. Si is bonded in a 9-coordinate geometry to three equivalent Gd and six equivalent Re atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Correlations for the specific heat capacity of ( U x Pu 1 - x ) 1 - y Gd y O 2 - z derived from molecular dynamics

We report UO 2 is the primary conventional fuel used in most nuclear reactors with Gd 2 O 3 commonly added as a burnable absorber to produce a more level power distribution in the reactor core at the beginning of operation. It can also be mixed with other actinide oxides to produce mixed oxide (MOx) fuel. In this study, molecular dynamics simulations were used to predict the specific heat capacity of Gd-doped PuO 2 , UO 2 and (U, Pu)O 2 MOx accommodating Gd 3+ substituted at cation sites via two charge compensation mechanisms - oxygen vacancy formation and the oxidation of U 4+ to U 5+ . The specific heat capacity values for PuO 2 and UO 2 are in good agreement with other studies showing a distinct peak at high temperatures - above 1800 K. As Gd 3+ is added, the peak height reduces for each composition considered. An analytical fit was applied to the data where Gd 3+ was fully charge compensated by either oxygen vacancies or U 5+ . The expression was then validated by predicting the specific heat capacity for three compositions of (Ux Pu 1-x ) 1-y Gd y O 2-z containing both oxygen vacancies and U 5+ , and compared to molecular dynamics data.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Influence of cation species on thermal expansion of Y 2 Si 2 O 7 –Gd 2 Si 2 O 7 solid solutions

Mixtures of Y 2 Si 2 O 7 and Gd 2 Si 2 O 7 were synthesized by solid-state reaction at 1600°C and characterized via in situ x-ray diffraction (XRD) to determine their coefficients of thermal expansion (CTE). All solid solutions within the system exhibited the orthorhombic δ-RE 2 Si 2 O 7 (Pna2 1 ) structure. Thermal expansion measurements of Y 2 Si 2 O 7 and Gd 2 Si 2 O 7 correlated well with reported values in literature, and all synthesized solid solutions exhibited CTEs between Y 2 Si 2 O 7 and Gd 2 Si 2 O 7 . Generally, there was a slight decrease in CTE exhibited by the materials with increasing Gd 2 Si 2 O 7 content, with Gd 2 Si 2 O 7 having the lowest CTEs and Y 2 Si 2 O 7 the highest CTEs. Here, the decrease in CTE was attributed to stronger bonds of Gd-O over Y-O, as determined by calculated crystal orbital Hamilton populations using density functional theory. However, such differences were very small and crystal structure was the dominating factor in CTE trends.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Role of element-specific damping in ultrafast, helicity-independent, all-optical switching dynamics in amorphous (Gd,Tb)Co thin films

Ultrafast control of the magnetization in ps timescales by fs laser pulses offers an attractive avenue for applications such as fast magnetic devices for logic and memory. However, ultrafast helicity-independent all-optical switching (HI-AOS) of the magnetization has thus far only been observed in Gd-based, ferrimagnetic amorphous (a-) rare earth-transition metal (a-RE-TM) systems, and a comprehensive understanding of the reversal mechanism remains elusive. Here, we report HI-AOS in ferrimagnetic a-Gd 22-x Tb x Co 78 thin films, from x=0 to 18, and elucidate the role of Gd in HI-AOS in a-RE-TM alloys and multilayers. Increasing Tb content results in increasing perpendicular magnetic anisotropy and coercivity, without modifying magnetization density, and slower remagnetization rates and higher critical fluences for switching but still shows picosecond HI-AOS. Simulations of the atomistic spin dynamics based on the two-temperature model reproduce these results qualitatively and predict that the lower damping on the RE sublattice arising from the small spin-orbit coupling of Gd (with L=0) is instrumental for the faster dynamics and lower critical fluences of the Gd-rich alloys. Annealing a-Gd 10 Tb 12 Co 78 leads to slower dynamics which we argue is due to an increase in damping. These simulations strongly indicate that accounting for element-specific damping is crucial in understanding HI-AOS phenomena. The results suggest that engineering the element-specific damping of materials can open up new classes of materials that exhibit low-energy, ultrafast HI-AOS.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Magnetic structure and exchange interactions in the Heisenberg pyrochlore antiferromagnet Gd 2 Pt 2 O 7

In this report the Heisenberg pyrochlore antiferromagnet Gd 2 Pt 2 O 7 is one of a series of gadolinium pyrochlore compounds with a variety of B-site cations. Despite the expected simplicity of a spin-only Gd 3+ Heisenberg interaction model, the gadolinium pyrochlore series exhibits various complex magnetic ground states at low temperature. Gd 2 Pt 2 O 7 displays the highest temperature magnetic order of the series with $T_N$=1.6 K, which has been attributed to enhanced superexchange pathways facilitated by empty $5d$ $e_g$ Pt orbitals. In this study, we use various neutron scattering techniques on an isotopically enriched polycrystalline 160 Gd 2 Pt 2 O 7 sample to examine the magnetic structure and spin-wave excitation spectrum below $T_N$ in order to extract the dominant exchange interactions. We find that the ground-state magnetic structure is the Palmer-Chalker state previously seen in Gd 2 Sn 2 O 7 with an associated gapped excitation spectrum consistent with enhanced exchange interactions between further near-neighbor Gd 3+ ions. We confirm this exchange model with analysis of the magnetic diffuse scattering in the paramagnetic regime using polarized neutrons.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on Gd(CuGe)2 by Materials Project

GdCu2Ge2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Gd is bonded in a 4-coordinate geometry to eight equivalent Cu and eight equivalent Ge atoms. There are a spread of Gd–Cu bond distances ranging from 3.23–3.36 Å. There are four shorter (3.12 Å) and four longer (3.20 Å) Gd–Ge bond lengths. Cu is bonded in a 4-coordinate geometry to four equivalent Gd and four equivalent Ge atoms. There are three shorter (2.45 Å) and one longer (2.46 Å) Cu–Ge bond lengths. Ge is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Cu, and one Ge atom. The Ge–Ge bond length is 2.49 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(SiRh)2 by Materials Project

GdRh2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent Si atoms. All Gd–Rh bond lengths are 3.24 Å. All Gd–Si bond lengths are 3.14 Å. Rh is bonded to four equivalent Gd and four equivalent Si atoms to form a mixture of distorted corner, edge, and face-sharing RhGd4Si4 tetrahedra. All Rh–Si bond lengths are 2.41 Å. Si is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Rh, and one Si atom. The Si–Si bond length is 2.47 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(SiPt)2 by Materials Project

GdPt2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 8-coordinate geometry to eight equivalent Pt and eight equivalent Si atoms. All Gd–Pt bond lengths are 3.25 Å. All Gd–Si bond lengths are 3.20 Å. Pt is bonded to four equivalent Gd and four equivalent Si atoms to form a mixture of distorted edge, corner, and face-sharing PtGd4Si4 tetrahedra. All Pt–Si bond lengths are 2.48 Å. Si is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Pt, and one Si atom. The Si–Si bond length is 2.36 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(CoGe)2 by Materials Project

GdCo2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 8-coordinate geometry to eight equivalent Co and eight equivalent Ge atoms. All Gd–Co bond lengths are 3.23 Å. All Gd–Ge bond lengths are 3.11 Å. Co is bonded to four equivalent Gd and four equivalent Ge atoms to form a mixture of distorted edge, face, and corner-sharing CoGd4Ge4 tetrahedra. All Co–Ge bond lengths are 2.34 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Co, and one Ge atom. The Ge–Ge bond length is 2.63 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(FeGe)2 by Materials Project

GdFe2Ge2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Gd is bonded in a 8-coordinate geometry to eight equivalent Fe and eight equivalent Ge atoms. There are a spread of Gd–Fe bond distances ranging from 3.30–3.37 Å. There are four shorter (3.08 Å) and four longer (3.09 Å) Gd–Ge bond lengths. Fe is bonded to four equivalent Gd and four equivalent Ge atoms to form a mixture of distorted edge, corner, and face-sharing FeGd4Ge4 tetrahedra. There are one shorter (2.43 Å) and three longer (2.44 Å) Fe–Ge bond lengths. Ge is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Fe, and one Ge atom. The Ge–Ge bond length is 2.54 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(NiGe)2 by Materials Project

GdNi2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 8-coordinate geometry to eight equivalent Ni and eight equivalent Ge atoms. All Gd–Ni bond lengths are 3.21 Å. All Gd–Ge bond lengths are 3.16 Å. Ni is bonded in a 4-coordinate geometry to four equivalent Gd and four equivalent Ge atoms. All Ni–Ge bond lengths are 2.37 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Ni, and one Ge atom. The Ge–Ge bond length is 2.55 Å.

36 MATERIALS SCIENCE↗