Search NASA⌕ Search

SEARCH · Search NASA

Results for “ionic bonding”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Revisiting the assignment of atomic charges in metal oxides based on core-level x-ray photoelectron spectra: The case of Ti in SrTiO3(001)

We demonstrate that assigning formal charges to transition metal (TM) cations based on core-level (CL) x-ray photoemission binding energies in oxides leads to physically inconsistent pictures of electronic structure. O 2p–TM 3d hybridization is well known to result in significant covalency in TM–O bonds, thereby reducing TM cation charges from their fully ionic values. However, the ionic bonding model remains the working paradigm for assigning TM CL features, and the resulting cation charges are often taken to be representative of the material under study. Here, we show that a more physically meaningful way to assign charges is to extract information about charge distributions utilizing Dirac–Hartree–Fock theory to calculate CL spectra from first principles and then use the resulting wave functions to determine charges based on orbital occupancies. TM cation charges can also be determined using density functional theory and Bader population analysis. We illustrate these two methods using the Ti 2p spectrum for SrTiO3(001) and show that the agreement between them is excellent. Significantly, the resulting Ti charge is considerably lower than the formal charge. The high degree of similarity between the Ti 2p spectrum for SrTiO3 and those for the rutile and anatase polymorphs of TiO2 suggests that the charge densities surrounding Ti in the latter materials are similar to that in SrTiO3. Taking a broader perspective, oxides containing other first-row transition metals also exhibit covalent character, leading to TM cation charges lower than the analogous fully ionic values in these materials as well.

Chambers, Scott A. (ORCID:000000025415043X)↗
DOE OSTI2017

CaCoSO diluted magnetic antiferromagnet semiconductor as efficient thermoelectric materials

Highlights: • CaCoSO exhibit direct (Γ{sup v}- Γ{sup c}) gap of about 2.187 eV for spin-up (↑). • CaCoSO exhibit direct (K{sup v}-K{sup c}) gap of about 1.187 eV for spin-down(↓). • An indirect gap (Γ{sup v}-K{sup c}) of about 0.4 eV for the spin-polarized CaCoSO. • Small gap turn CaCoSO to be as promising candidate for thermoelectric materials. - Abstract: We have reported the thermoelectric properties of the recently synthesized CaCoSO single crystal by Salter et al. in 2016. It is quite interesting to mention that CaCoSO single crystals exhibit a direct energy gap (Γ{sup v}- Γ{sup c}) of about 2.187 eV for the spin-up (↑) channel, which turns out to be a (K{sup v}-K{sup c}) direct gap of about 1.187 eV for the spin-down (↓) channel, resulting in an indirect gap (Γ{sup v}-K{sup c}) of about 0.4 eV for the spin-polarized CaCoSO single crystal. Such a small gap makes CaCoSO a promising candidate for thermoelectric materials. Calculations reveal a remarkable finding that the CaCoSO single crystal exhibits high electrical conductivity, low thermal conductivity and a large Seebeck coefficient; therefore, based on these findings, the CaCoSO single crystal may be considered an efficient thermoelectric material. The electron clouds of CaO{sub 3}S{sub 4} and CoS{sub 3}O exhibit a planar shape with conjugated electron orbitals and exhibit a strong covalent Ca−O, Co−O bonding. This is another factor which makes CaCoSO a promising candidate for thermoelectric materials, since covalent bonding is more favorable for the transport of the carriers than ionic bonding. CaO{sub 3}S{sub 4} and CoS{sub 3}O are the main sources for the thermoelectric generator in CaCoSO. Therefore, based on the above findings, we can conclude that CaCoSO could be a promising thermoelectric material.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Blending Ionic and Coordinate Bonds in Hybrid Semiconductor Materials: A General Approach toward Robust and Solution-Processable Covalent/Coordinate Network Structures

Inorganic semiconductor materials are best known for their superior physical properties, as well as their structural rigidity and stability. However, the poor solubility and solution-processability of these covalently bonded network structures has long been a serious drawback that limits their use in many important applications. Here, we present a unique and general approach to synthesize robust, solution-processable, and highly luminescent hybrid materials built on periodic and infinite inorganic modules. Structure analysis confirms that all compounds are composed of one-dimensional anionic chains of copper iodide (Cu m I m+2 2- ) coordinated to cationic organic ligands via Cu-N bonds. The choice of ligands plays an important role in the coordination mode (μ 1 -MC or μ 2 -DC) and Cu-N bond strength. Greatly suppressed nonradiative decay is achieved for the μ 2 -DC structures. Record high quantum yields of 85% (λ ex = 360 nm) and 76% (λ ex = 450 nm) are obtained for an orange-emitting 1D-Cu 4 I 6 (L 6 ). Temperature dependent PL measurements suggest that both phosphorescence and thermally activated delayed fluorescence contribute to the emission of these 1D-AIO compounds, and that the extent of nonradiative decay of the μ 2 -DC structures is much less than that of the μ1 -DC structures. More significantly, all compounds are remarkably soluble in polar aprotic solvents, distinctly different from previously reported CuI based hybrid materials made of charge-neutral Cu m X m (X = Cl, Br, I), which are totally insoluble in all common solvents. Finally, the greatly enhanced solubility is a result of incorporation of ionic bonds into extended covalent/coordinate network structures, making it possible to fabricate large scale thin films by solution processes

36 MATERIALS SCIENCE↗
DOE OSTI2025

Multistage nucleation pathway in LiF molten salt mirrors the crystal–melt interface structure

Despite over a century of studies, fundamental questions remain about the processes governing crystal nucleation from melts or solutions. Research over the past three decades has presented mounting evidence for kinetic pathways of crystal nucleation that are more complex than envisioned by the simplest forms of classical theory. Such observations have been presented for colloidal and elemental systems with covalent and metallic bonding. Despite the technological and geochemical importance of molten salts, similar studies for these ionically bonded systems are currently lacking. Here we develop a machine learning interatomic potential for a model ionic system: LiF. The potential features quantum-level accuracy for both liquid and multiple solid polymorphs over wide temperature and pressure ranges and accurately reproduces experimentally measured properties. Thanks to the efficiency of the potential, which enables microsecond-scale molecular dynamics simulations, induction times for nucleation of LiF solids from their melts are computed over a range of undercoolings. With the aid of a set of robust local order parameters established here, the simulations reveal that homogeneous crystal nucleation in undercooled melts preferentially initiates from liquid regions showing slow dynamics and high bond orientational order simultaneously, and the second-shell order of both precritical nuclei and the surface of postcritical nuclei is dominated by hexagonal close packing and body-centered cubic local structure, even though the nucleus core is dominated by face-centered cubic structure corresponding to the stable rocksalt crystal structure. Finally, we establish a connection between the crystallization pathway and the equilibrium crystal-melt interface structure.

Applied Physical Sciences↗
DOE OSTI2018

Polarity governs atomic interaction through two-dimensional materials

The objective of this project is to develop two-dimensional material-based layer transfer (2DLT) for high-efficiency, low-cost III-V solar cells. More specifically, in short term, the team will develop 2DLT for cost-cost, high-throughput GaAs single-junction solar cells. The team will develop ultraclean high yield graphene transfer on GaAs and optimize the remote homoepitaxy process to obtain dislocation-free single-crystalline GaAs on graphene whose crystalline quality is identical to that of the GaAs wafer [1,2]. The team will develop the 2DLT process for a solar cell with highest achievable efficiency. The team will also strive to target GaAs solar cells with efficiency of 25~29% before and after the transfer, and reuse the substrate multiple times without CMP by damage-free transfer process enabled by 2DLT. Our team is partnered with industrial collaborators to obtain World record efficiency of flexible GaAs solar cells. Once the concept is fully realized for the GaAs solar cells, the team will expand the concept for multiple-junction solar cell targeting 35% efficiency with the 2DLT process in other projects.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Insights into the Enhanced Oxidative Thermal Stability of Nanoparticle Organic Hybrid Materials Developed for Carbon Capture and Energy Storage

Due to the growing need for Direct Air Capture (DAC) and integrated carbon capture and conversion technologies, CO 2 capture materials that can withstand a wide range of environmental conditions, including fluctuating ambient temperatures and high concentrations of oxidizing agents (i.e., oxygen and moisture), are critically needed. Liquid-like Nanoparticle Organic Hybrid Materials (NOHMs) have been proposed as candidates for DAC and electrolyte additives enabling sustainable energy storage (i.e., integrated CO 2 capture and conversion and flow batteries). Liquid-like NOHMs functionalized with an ionic bond have been shown to display greatly enhanced oxidative thermal stability compared to the untethered polymer. However, these studies were limited in terms of reaction conditions and the detailed mechanisms of the oxidative thermal degradation were not reported. In this work, a kinetic thermal degradation analysis was performed on NOHM-I-HPE and the neat polymer, Jeffamine M2070 (HPE), in both non-oxidative and oxidative conditions. NOHM-I-HPE displayed similar thermal stability to the untethered polymer in a nitrogen environment, but interestingly, the thermal stability of the ionically tethered polymer was significantly enhanced in the presence of air. This observed enhancement of oxidative thermal stability is attributed to the orders of magnitude larger viscosity of the liquid-like NOHMs compared to untethered polymer and the bond stabilization of the ionically tethered polymer in the NOHMs canopy. Further, spectroscopic analyses of the liquid residue revealed that in the presence of oxygen, the degradation of HPE and NOHM-I-HPE occurs through the formation of trace amounts of carbonyls. This study illustrated that NOHMs can serve as functional materials for sustainable energy storage applications because of their excellent oxidative thermal stability.

25 ENERGY STORAGE↗
DOE OSTI2020

Roles of Alkali Metals and Ionic Networks in Directing the Formation of Anionic Metal–Organic Frameworks

Integrating different types of fundamental chemical interactions to direct the self-assembly processes and to control the dimension of the network formed by each type of interactions is a promising strategy to develop advanced functional materials. Here, the ionic interaction of alkali metals (Na, K, Cs) towards multi-functional 2,2’-disulfo-4,4’-oxydibenzoic acid is utilized in two solvent systems, aqueous-amide and uro-amide, to synthesize six novel anionic framework materials with dramatically different features and dimensionalities: (Na 3 [Zn 4 O(L 4- ) 3 (e-murea)(H 2 O) 3 ](H 2 N(CH 3 ) 2 +) 3 (CPM-s1), [Zn 4 O(L 4- ) 3 (DMF)]((NH 2 (CH 3 ) 2 +) 6 ) (CPM-s2), Na 6 [(Zn 2 OH 2 ) 3 (L 3- ) 6 ](H 2 O) 3 (CPM-s3), K 3 [Zn 2 (L 4- ) 2 ](H 2 N(CH 3 ) 2 +)(e-murea) 2 (H 2 O) 3 (CPM-s4), K 4 [Zn(L 3- ) 2 ](H 2 O) 2 (CPM-s5), and Cs 6 [Zn(L 4- ) 2 ](H 2 O) 2 (CPM-s6), L 4- = 2,2’-disulfo-4,4’-oxydibenzoate, DMF = N,N-dimethylformamide, e-murea = 1,3-dimethyl-1-2-imidazolidinone). In CPM-s1 to CPM-s6, the alkali-sulfonate ionic bonding networks transformed from 0D clusters with Na + to 1D chains and 2D sheets with K + , and 3D network with Cs + . These vastly differing ionic domains influenced the coordination modes and spatial arrangements of the metal-carboxylate linkers, which consequently, directed the dimensionality of the coordination networks from 3D with Na + to 1D with Cs + . CPM-s1 and CPM-s2, made from tetrameric Zn 4 O clusters are rare examples of anionic MOF-5-type structures. CPM-s3 features an unprecedented hexameric Zn 6 cluster. Even though a large portion of the charge-balancing cations in these materials would hamper hydrogen bonding networks, some of them still exhibit very high ionic conductivity (e.g. 1.25 x 10 -3 S cm -1 in CPM-s3), suggesting the potential of these materials as solid-state electrolytes.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Impacts of Bond Type and Grafting Density on the Thermal, Structural, and Transport Behaviors of Nanoparticle Organic Hybrid Materials–Based Electrolytes

Nanoscale Organic Hybrid Materials (NOHMs) consist of polymers tethered to a nanoparticle surface, and NOHMs formed with an ionic bond between the polymer and nanoparticle have been proposed for electrochemical applications. NOHMs exhibit negligible vapor pressure, chemical tunability, oxidative thermal stability, and high ionic conductivity making them attractive in reactive and separation systems. In this study, NOHMs are synthesized by tethering Jeffamine M2070 (HPE) to SiO 2 nanocores via ionic (NOHM-I-HPE) and covalent (NOHM-C-HPE) bonding to investigate the effect of the bond type on the thermal, structural and transport properties of the tethered HPE. In the neat state, NOHM-C-HPE displays the highest thermal stability in a nitrogen atmosphere, while NOHM-I-HPE is the most stable under oxidative conditions. Small-angle neutron scattering (SANS) reveals the presence of multiple types of HPE polymers in aqueous solutions of NOHM-I-HPE (i.e., tethered, interacting, and free), whereas only tethered HPE is observed in NOHM-C-HPE systems. Moreover, the SANS profiles identify clustering of NOHM-C-HPE in aqueous solutions, but not in the corresponding NOHM-I-HPE solutions, suggesting that the free HPE chains stabilize the dispersion of NOHM-I-HPE. Furthermore, the results of this study elucidate how the bond type and grafting density can be used to tune the properties of NOHMs.

25 ENERGY STORAGE↗
DOE OSTI2025

Electronic Configurational Transformation of Network Modifiers in Aluminate Glass above Megabar Pressures

Electronic responses of glasses under extreme pressures differ from those of crystalline analogs. Their distinct electronic environments are found in network formers with well-defined, covalent-bonded coordination environments (e.g., [4] Si and [4] Al) and in network modifiers with more disordered, ionic-bonded configurations (e.g., [5,6,7] Ca). Deciphering the evolution of the bonding environment of network modifier cations upon compression provides atomic insights into the pressure-driven hardening and transport properties of glasses. Despite the importance, in contrast to extensive efforts to uncover how network formers behave under pressure, considerable structural disorder around network modifiers makes it challenging to probe their electronic bonding environments under compression. Our understanding of the evolution of network modifiers above megabars is currently absent. Here, we report a discovery of highly densified electronic configurations of network modifier Ca in aluminate glass under extreme compression via the first inelastic X-ray scattering at the Ca L-edge up to 140 GPa. As evidenced by the prominent pressure-driven increases in electronic dispersion and delocalization, densified calcium environments are characterized by a decreased average Ca–O distance, the formation of highly coordinated calcium, a broader distribution of topological variables, and a greater distortion of Ca polyhedra above megabars. The spectral features for the Ca environments reveal significant electronic and bonding modifications, including pressure-driven increases in the ligand field interaction, the covalence characteristic of the Ca–O bond, and the electron–hole Coulomb interaction. These densification paths identify the electronic adaptation of network modifiers above megabars, shedding light on the origins of enhanced electron transport and the electron-storing capacity of glasses under pressure.

amorphous materials↗
DOE OSTI2019

Toward a Reversible Calcium-Sulfur Battery with a Lithium-Ion Mediation Approach

Calcium represents a promising anode for the development of high-energy-density, low-cost batteries. Yet, a lack of suitable electrolytes has restricted the development of rechargeable batteries with a Ca anode. Furthermore, to achieve a high energy density system, sulfur would be an ideal cathode to couple with the Ca anode. Unfortunately, a reversible calcium-sulfur (Ca-S) battery has not yet been reported. Herein, a basic study of a reversible nonaqueous room-temperature Ca-S battery is presented. The reversibility of the Ca-S chemistry and high utilization of the sulfur cathode are enabled by employing a Li + -ion-mediated calcium-based electrolyte. Mechanistic insights pursued by spectroscopic, electrochemical, microscopic, and theoretical simulation (density functional theory) investigations imply that the Li + -ions in the Ca-electrolyte stimulate the reactivation of polysulfide/sulfide species. The coordination of lithium to sulfur reduces the formation of sturdy Ca-S ionic bonds, thus boosting the reversibility of the Ca-S chemistry. Furthermore, the presence of Li + -ions facilitates the ionic charge transfer both in the electrolyte and across the solid electrolyte interphase layer, consequently reducing the interfacial and bulk impedance of Ca-S batteries. As a result, both the utilization of active sulfur in the cathode and the discharge voltage of Ca-S batteries are significantly improved.

25 ENERGY STORAGE↗
NASA NTRS1984

Mean excitation energies for stopping powers in various materials composed of elements hydrogen through argon

The local plasma model is used to study the effects of the chemical and physical state of a medium on its stopping power. The relationship between that model and a more exact quantum treatment of bound systems is elucidated by examining related quantities in both theories for the case of one and two-electron systems. Atomic mean excitation energies and straggling parameters in the local plasma model are compared with the accurate calculations of Inokuti et al. (1975, 1978, 1981). The use of the Gordon-Kim electron gas model of molecular bonding is used to determine the effects of covalent chemical bond shifts on the mean excitation energies for elements of the first two rows. Calculations of mean excitation energies of ionic bonded substances are presented, and the mean excitation energies of metals are discussed.

Wilson, J. W.↗
DOE OSTI2017

Reaction of benzylidenetriphenylphosphorane with 1,4-dichloro-3а,6а-diaza-1,4-diphosphapentalene

The transylidation between 1,4-dichloro-3a,6a-diaza-1,4-diphosphapentalene and benzylidenetriphenylphosphorane (Ph{sub 3}P=CHPh) results in either mono- or disubstitution of chlorine atoms by the Ph{sub 3}P=C(Ph) group depending on the reactant molar ratio. In the crystal, the monosubstituted product has the planar diazadiphosphapentalene ring and the P—Cl ionic bond. The {sup 31}P NMR spectra of this compound exhibit a strong solvent-dependent behavior, which indicates that it exists both in the ionic form (in CH{sub 2}Cl{sub 2}, MeCN) and the molecular form (in THF). In the disubstituted product, the diazadiphosphapentalene skeleton is non-planar and is bent along the N—N bond.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Insight into the Structural and Emissive Behavior of a Three‐Dimensional Americium(III) Formate Coordination Polymer

Abstract We report the structural, vibrational, and optical properties of americium formate (Am(CHO 2 ) 3 ) crystals synthesized via the in situ hydrolysis of dimethylformamide (DMF). The coordination polymer features Am 3+ ions linked by formate ligands into a three‐dimensional network that is isomorphous to several lanthanide analogs, (e. g., Eu 3+ , Nd 3+ , Tb 3+ ). Structure determination revealed a nine‐coordinate Am 3+ metal center that features a unique local C 3v symmetry. The metal–ligand bonding interactions were investigated by vibrational spectroscopy, natural localized molecular orbital calculations, and the quantum theory of atoms in molecules. The results paint a predominantly ionic bond picture and suggest the metal‐oxygen bonds increase in strength from Nd−O 5 D 1′ → 7 F 0′ emission band is observed and dominates the emission spectrum. This behavior is unusual and is attributed to the C 3v coordination environment of the metal center.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Electron Configurations and Basic Chemical Bonding

The goal of this lecture is to cover the basics of atomic electrons: Definitions of shells, subshells, and orbitals; Max number of electrons per subshell; Order of filling shells; The Periodic Table and electron configuration; and Covalent and Ionic Bonding.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Optimization of the Reax force field for the lithium–oxygen system using a high fidelity charge model

Studies using molecular dynamics (MD) have long struggled to simulate the failure modes of materials, predicting unrealistically high ductility and failing to capture brittle fracture. The primary cause of this shortcoming is an inadequate description of bond breaking. While reactive force fields such as ReaxFF show improvements compared to traditional force fields, the charge models used yield unphysical partial charges, especially during dissociation of ionic bonds. This flaw may be remedied by using the atom-condensed Kohn–Sham density functional theory (DFT) approximated to a second order (ACKS2) charge model for determining partial charges. In this work, we present a new ACKS2-enabled Reax force field for fracture simulations of lithium oxide systems, which was obtained by training against an extensive set of DFT, multireference configuration interaction (MRCI), and MRCI+Q reference data using genetic optimization techniques. This new force field significantly improves the bond breaking behavior, but still cannot fully capture the brittle fracture in MD simulations, suggesting more research is needed to improve simulation of brittle fracture.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Nature of the bonded-to-atomic transition in liquid silica to TPa pressures

First-principles calculations and analysis of the thermodynamic, structural, and electronic properties of liquid SiO 2 characterize the bonded-to-atomic transition at 0.1–1.6 TPa and 10 4 –10 5 K (1–9 eV), the high-energy-density regime relevant to understanding planetary interiors. We find strong ionic bonds that become short-lived due to high kinetics during the transition, with sensitivity of the transition temperature to pressure, and our calculated Hugoniots agree with past experimental data. Furthermore, these results reconcile previous experimental and theoretical findings by clarifying the nature of the bond dissociation process in early Earth and “rocky” (oxide) constituents of large planets.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2022

Revisiting W–ZrC interfaces: A first principles study

We investigate W–ZrC interfaces using first-principles calculations based on the density functional theory. There have been theoretical and experimental studies exploring W–ZrC interfaces, however, the debate regarding the most stable interface continues to persist. In this study, we systematically simulated various W–ZrC interfaces merging W and ZrC surfaces with different orientations. Subsequently, we evaluated their stabilities and explained the corresponding stabilities in terms of the nature of bonding and charge-transfer processes at the interface. We find ZrC(111)–W(110) is the most stable interface with higher adhesive energy than the other interfaces. The additional stability associated with the ZrC(111)–W(110) results from significant interface reconstruction. Three layers of W and ZrC adjacent to the interface are involved in the charge-transfer process leading to stronger ionic bonds in ZrC(111)–W(110) as compared to the other potential candidate: ZrC(100)–W(100). The C and W atoms are found to be displaced from their symmetric position during the reconstruction process at the interface to facilitate stronger bonds with shorter W–C and W–Zr bonds in ZrC(111)–W(110) as compared to ZrC(100)–W(100). This leads to stronger covalent bonds in ZrC(111)–W(110) than that in ZrC(100)–W(100). Therefore, we conclude that the stronger covalent and ionic forces in ZrC(111)–W(110) than those in ZrC(100)–W(100) are responsible for making ZrC(111)–W(110) to be the most stable interface. In conclusion, this study addresses the long-standing question of the most stable W–ZrC interface and derives a number of implications for other W-transition metal carbide interfaces which are potential candidates for improving the mechanical properties of plasma facing materials.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Gamma Irradiation of Novel Optical Glasses at Elevated Temperature

Advanced Small Modular Reactors (AdvSMRs) are considered important future energy sources. However, in-vessel radiation fluxes are high and demands infrared (IR) optical fiberbased chemical sensing at temperatures that often exceed 400°C. This is a challenging environment for many current IR glasses, including covalently-bonded selenides and tellurides, such as As2Se3 and GeTe2, due their glass transition temperatures (Tg) being on the order of 200-350 °C. This work focuses on ?-irradiation affects at high temperatures on refractory ionic bonding based chalcogenide glasses in the BaS-La2S3-GeS2 system. Optical and selected physical properties were characterized before and after irradiation. It was found that both GeS2 and the 20BaS + 20La2S3 + 60GeS2 composition (in mole%) have minimal property changes when irradiated at 2.5 MGy cumulative dose at 300 °C. Sample density showed the largest characteristic change where densities initially decreased at 2 kGy dose, and then recovered at the highest dose of 2.5 MGy, resulting in an overall density change between 0.3 to 2%, depending on sample and composition. This work suggests the BaS-La2S3-GeS2 system as one for continued exploration as high temperature IR fiber sensors in radiation environments.

Gamma Irradiation, Novel Optical Glasses, Elevated↗