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All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

The Keck Task Library (KTL)

KTL is a set of routines which eases the job of writing applications which must interact with a variety of underlying sub-systems (known as services). A typical application is an X Window user interface coordinating telescope and instruments. In order to connect to a service, application code specifies a service name--typically an instrument name--and a style, which defines the way in which the application will interact with the service. Two styles are currently supported: keyword, where the application reads and writes named keywords and the resulting inter-task message traffic is hidden; and message, where the application deals directly with messages. The keyword style is intended mainly for user interfaces, and the message style is intended mainly for lower-level applications. KTL applications are event driven: a typical application first connects to all its desired services, then expresses interest in specified events. The application then enters an event dispatch loop in which it waits for events and calls the appropriate service's event-handling routine. Each event is associated with a call-back routine which is invoked when the event occurs. Call-back routines may (and typically do) interact with other sub-systems and KTL provides the means of doing so without blocking the application (vital for X Window user interfaces). This approach is a marriage of ideas culled from the X window, ADAM, Keck instrument, and Keck telescope control systems. A novel feature of KTL is that it knows nothing about any services or styles. Instead it defines a generic set of routines which must be implemented by all services and styles (essentially open(), ioctl(), read(), write(), event(), and close()) and activates sharable libraries at run-time. Services have been implemented (in both keyword and message styles) for HIRES (the Keck high resolution echelle spectrograph built by Lick Observatory), LWS (the Keck long wavelength spectrometer built by UC San Diego), and the Keck telescope. Each of these implementations uses different underlying message systems: the Lick MUSIC system, RPC's, and direct sockets (respectively). Services for the remaining three front-line Keck instruments will be implemented over the next few months.

Lupton, W. F.↗
DOE OSTI2020

Materials Data on KTl(CN)4 by Materials Project

KTl(CN)4 crystallizes in the tetragonal I4_1/a space group. The structure is three-dimensional and consists of two KTl(CN)4 frameworks. K1+ is bonded in a tetrahedral geometry to four equivalent N3- atoms. All K–N bond lengths are 2.90 Å. Tl1+ is bonded in a tetrahedral geometry to four equivalent C+2.50+ atoms. All Tl–C bond lengths are 2.21 Å. C+2.50+ is bonded in a linear geometry to one Tl1+ and one N3- atom. The C–N bond length is 1.17 Å. N3- is bonded in a distorted bent 120 degrees geometry to one K1+ and one C+2.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KTl by Materials Project

KTl crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of two KTl sheets oriented in the (0, 0, 1) direction. K is bonded in a 6-coordinate geometry to six equivalent Tl atoms. All K–Tl bond lengths are 3.76 Å. Tl is bonded in a 9-coordinate geometry to six equivalent K and three equivalent Tl atoms. All Tl–Tl bond lengths are 3.13 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KTl by Materials Project

KTl crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are three inequivalent K sites. In the first K site, K is bonded in a 4-coordinate geometry to four equivalent Tl atoms. There are two shorter (3.75 Å) and two longer (3.81 Å) K–Tl bond lengths. In the second K site, K is bonded in a 6-coordinate geometry to six Tl atoms. There are a spread of K–Tl bond distances ranging from 3.71–3.93 Å. In the third K site, K is bonded in a 6-coordinate geometry to six Tl atoms. There are a spread of K–Tl bond distances ranging from 3.70–4.06 Å. There are two inequivalent Tl sites. In the first Tl site, Tl is bonded in a 8-coordinate geometry to four K and four equivalent Tl atoms. There are two shorter (3.15 Å) and two longer (3.17 Å) Tl–Tl bond lengths. In the second Tl site, Tl is bonded in a 8-coordinate geometry to six K and two equivalent Tl atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KTl(CoSe)4 by Materials Project

KTl(CoSe)4 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. K1+ is bonded in a body-centered cubic geometry to eight equivalent Se2- atoms. All K–Se bond lengths are 3.41 Å. Co+1.50+ is bonded to four Se2- atoms to form a mixture of edge and corner-sharing CoSe4 tetrahedra. There are two shorter (2.34 Å) and two longer (2.35 Å) Co–Se bond lengths. Tl1+ is bonded in a body-centered cubic geometry to eight equivalent Se2- atoms. All Tl–Se bond lengths are 3.42 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to four equivalent Co+1.50+ and four equivalent Tl1+ atoms. In the second Se2- site, Se2- is bonded in a 8-coordinate geometry to four equivalent K1+ and four equivalent Co+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Heterostructured Lepidocrocite Titanate-Carbon Nanosheets for Electrochemical Applications

Lepidocrocite-type titanates that reversibly intercalate sodium ions at low potentials (~0.6 V vs Na/Na + ) are promising anode candidates for sodium-ion batteries. However, large amounts of carbon additives are often used to improve their electrical conductivity and overcome poor cycling performance in the electrode composites. To ameliorate electronic transport issues of lepidocrocite titanate (K 0.8 Ti 1.73 Li 0.27 O 4 , KTL) in sodium-ion batteries, we have designed and synthesized heterostructures of exfoliated lepidocrocite-type titanium oxide (LTO) nanosheets with alternating carbon layers via a solution-based self-assembly approach. Positively charged dopamine (Dopa) was used as the carbon precursor and intercalated between negatively charged exfoliated titania nanosheets through electrostatic interaction. Dopa-intercalated LTO was then annealed under argon to form conductive carbon layers between titania sheets. The carbon content in the heterostructures was controlled by modifying the self-assembly conditions (i.e., pH, stirring duration, and Dopa-to-LTO ratio). Electrodes were prepared using carbonized heterostructures (LTO-C) without adding more carbon to the composites and tested in sodium half-cell configurations. Further, higher capacities and improved capacity retention over 250 cycles and lower impedance were observed, as the carbon content of LTO-C heterostructures was increased from 0% (LTO nanosheets) to 30%. These results indicate that the self-assembly approach for 2D heterostructured electrode materials is a promising strategy to overcome electronic transport limitations of layered transition-metal oxides and improve their electrochemical performance for next-generation energy storage applications.

25 ENERGY STORAGE↗
DOE OSTI2021

Tutorial on Chemical Pressure Analysis: How Atomic Packing Drives Laves/Zintl Intergrowth in K3Au5Tl

The tight atomic packing generally exhibited by alloys and intermetallics can create the impression of their being composed of hard spheres arranged to maximize their density. As such, the atomic size factor has historically been central to explanations of the structural chemistry of these systems. However, the role atomic size plays structurally has traditionally been inferred from empirical considerations. The recently developed DFT-Chemical Pressure (CP) analysis has opened a path to investigating these effects with theory. In this article, we provide a step-by-step tutorial on the DFT-CP method for non-specialists, along with advances in the approach that broaden its applicability. A new version of the CP software package is introduced, which features an interactive system that guides the user in preparing the necessary electronic structure data and generating the CP scheme, with the results being readily visualized with a web browser (and easily incorporated into websites). For demonstration purposes, we investigate the origins of the crystal structure of K3Au5Tl, which represents an intergrowth of Laves and Zintl phase domains. Here, CP analysis reveals that the intergrowth is supported by complementary CP features of NaTl-type KTl and MgCu2-type KAu2 phases. In this way, K3Au5Tl exemplifies how CP effects can drive the merging for geometrical motifs derived from different families of intermetallics through a mechanism referred to as epitaxial stabilization.

36 MATERIALS SCIENCE↗