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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Time-resolved simplified chemical kinetics modelling using computational singular perturbation

A CO-CH4-air reaction system is used to demonstrate the computational singular perturbation (CSP) method for deriving time-resolved simplified chemical kinetics models. CSP provides a programmable algorithm to group the given collection of elementary reactions into reaction groups which are ordered according to their speed. The concept of Importance Index k(m)exp s is introduced: k(m)exp s is defined to be a number between 0 and 1 which measures the importance of the m-th reaction group to the s-th reactant and can readily be computed from data generated by CSP. It is suggested that the robustness of the solutions of the reaction system can be qualitatively assessed by inspecting the Importance Index data.

Lam, S. H.↗
DOE OSTI2020

Materials Data on ThS2 by Materials Project

ThS2 is Cotunnite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Th4+ is bonded in a 9-coordinate geometry to nine S2- atoms. There are a spread of Th–S bond distances ranging from 2.81–3.29 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to five equivalent Th4+ atoms. In the second S2- site, S2- is bonded to four equivalent Th4+ atoms to form a mixture of edge and corner-sharing STh4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th2S5 by Materials Project

Th2S5 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. Th4+ is bonded in a 10-coordinate geometry to ten S+1.60- atoms. There are a spread of Th–S bond distances ranging from 2.88–3.15 Å. There are three inequivalent S+1.60- sites. In the first S+1.60- site, S+1.60- is bonded in a 4-coordinate geometry to four equivalent Th4+ atoms. In the second S+1.60- site, S+1.60- is bonded in a 6-coordinate geometry to four equivalent Th4+ and one S+1.60- atom. The S–S bond length is 2.16 Å. In the third S+1.60- site, S+1.60- is bonded in a 4-coordinate geometry to four equivalent Th4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th2S3 by Materials Project

Th2S3 is Stibnite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Th sites. In the first Th site, Th is bonded in a 7-coordinate geometry to eight S atoms. There are a spread of Th–S bond distances ranging from 2.87–3.48 Å. In the second Th site, Th is bonded to seven S atoms to form a mixture of distorted edge and corner-sharing ThS7 pentagonal bipyramids. There are a spread of Th–S bond distances ranging from 2.85–2.90 Å. There are three inequivalent S sites. In the first S site, S is bonded to five Th atoms to form a mixture of edge and corner-sharing STh5 square pyramids. In the second S site, S is bonded to five Th atoms to form a mixture of distorted edge and corner-sharing STh5 trigonal bipyramids. In the third S site, S is bonded in a distorted rectangular see-saw-like geometry to five Th atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThS by Materials Project

ThS is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Th is bonded to six equivalent S atoms to form a mixture of edge and corner-sharing ThS6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Th–S bond lengths are 2.86 Å. S is bonded to six equivalent Th atoms to form a mixture of edge and corner-sharing STh6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th3S by Materials Project

Th3S is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Th sites. In the first Th site, Th is bonded to four equivalent S atoms to form a mixture of distorted edge and corner-sharing ThS4 cuboctahedra. All Th–S bond lengths are 3.41 Å. In the second Th site, Th is bonded in a square co-planar geometry to four equivalent S atoms. All Th–S bond lengths are 3.30 Å. S is bonded to twelve Th atoms to form a mixture of edge, face, and corner-sharing STh12 cuboctahedra.

36 MATERIALS SCIENCE↗