Effect of light gas atom inclusions on the characteristics of laser-produced plasma ions

Khaydarov, R. T.; Beisinbaeva, H.B.; Sabitov, M.M.; Kalal, M.; Berdiyorov, Golibjon

doi:10.1088/0029-5515/51/10/103041

Cited by 3 publications

(7 citation statements)

References 14 publications

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“…The second attached lithium, forming Li2TiO2, remains fully ionized in a linear LiOTiOLi configuration in which it donates about 0.4 of its valence electron to Ti and the rest to O atoms whose Bader charge passes from −1.22 in linear OTiO to about −1.75 in LiOTiOLi. There is thus significant contribution from oxygen (16,14) curve is scaled by a factor of 0.3 for a better comparison. The gray, dashed lines indicate the cumulative numbers of electrons within the spheres of corresponding radii.…”

Section: Charge Distribution In Titanium Dioxide and Its Changes Upon Reductionmentioning

confidence: 99%

“…To give an illustrative example, consider Ti ions. Laser irradiation of titanium can create plasma in which Ti ions with different charge states can be reliably detected, including 0, +1, …+4 | e |, as well as higher charge states [ 13 , 14 ]. These actual charge states of isolated Ti ions, including Ti 4+ , are equal to their formal oxidation states.…”

Section: Introductionmentioning

confidence: 99%

“…The O atoms are located at r = 1.96 A in rutile and r = 1.95 and 2.01 Å in anatase. Bottom panels: spherically averaged valence electron density of a linear and bent TiO 2 molecule obtained with B3LYP, CAS(14,16), CCSD, and DFT PBE. The CAS(16,14) curve is scaled by a factor of 0.3 for a better comparison.…”

mentioning

confidence: 99%

“…Bottom panels: spherically averaged valence electron density of a linear and bent TiO 2 molecule obtained with B3LYP, CAS(14,16), CCSD, and DFT PBE. The CAS(16,14) curve is scaled by a factor of 0.3 for a better comparison. The gray, dashed lines indicate the cumulative numbers of electrons within the spheres of corresponding radii.…”

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confidence: 99%

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Density-Based Descriptors of Redox Reactions Involving Transition Metal Compounds as a Reality-Anchored Framework: A Perspective

et al. 2021

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Description of redox reactions is critically important for understanding and rational design of materials for electrochemical technologies, including metal-ion batteries, catalytic surfaces, or redox-flow cells. Most of these technologies utilize redox-active transition metal compounds due to their rich chemistry and their beneficial physical and chemical properties for these types of applications. A century since its introduction, the concept of formal oxidation states (FOS) is still widely used for rationalization of the mechanisms of redox reactions, but there exists a well-documented discrepancy between FOS and the electron density-derived charge states of transition metal ions in their bulk and molecular compounds. We summarize our findings and those of others which suggest that density-driven descriptors are, in certain cases, better suited to characterize the mechanism of redox reactions, especially when anion redox is involved, which is the blind spot of the FOS ansatz.

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Section: Charge Distribution In Titanium Dioxide and Its Changes Upon Reductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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Density-Based Descriptors of Redox Reactions Involving Transition Metal Compounds as a Reality-Anchored Framework: A Perspective

et al. 2021

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“…The O atoms are located at r = 1.96 A in rutile and r = 1.95 and 2.01 Å in anatase. Bottom panels: spherically averaged valence electron density of a linear and bent TiO2 molecule obtained with B3LYP, CAS(14,16), CCSD, and DFT PBE. The CAS(16,14) curve is scaled by a factor of 0.3 for a better comparison.…”

mentioning

confidence: 99%

Density-based Descriptors of Redox Reactions Involving Transition Metal Compounds as a Reality-anchored Framework: A Perspective

Koch¹,

Chaker²,

Ihara³

et al. 2021

Preprint

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Description of redox reactions is critically important for understanding and rational design of materials for electrochemical technologies including metal-ion batteries, catalytic surfaces, or redox-flow cells. Most of these technologies utilize redox-active transition metal compounds due to their rich chemistry and their beneficial physical and chemical properties for these types of applications. A century since its introduction, the concept of formal oxidation states (FOS) is still widely used for rationalization of the mechanisms of redox reactions, but there exists a well-documented discrepancy between FOS and the electron density-derived charge states of transition metal ions in their bulk and molecular compounds. We summarize our findings and those of others which suggest that density-driven descriptors are in certain cases better suited to characterize the mechanism of redox reactions, especially when anion redox is involved, which is the blind spot of the FOS ansatz.

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Addition to “On the Charge State of Titanium in Titanium Dioxide”

Koch¹,

Manzhos²

2017

J. Phys. Chem. Lett.

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W e provide here additional context to support the conclusion that we reached 1 that "Ti 3+ " (if one is to use an integer although charge quantization is not required here) is a better description of Ti in TiO 2 than "Ti 4+ ". Raebiger et al. 2 showed that the charge on a transition metal atom in a compound is very stable with respect to changes of the formal oxidation state (FOS) due to the so-called negative-feedback charge regulation. In ref 3, charge reporter molecules were used to reach a similar conclusion; specifically for Ti, a charge state of about +3 |e| was estimated. 3 Earlier, Christensen and Carter reported significant covalent character of bonds in ZrO 2 and concluded that in ZrO 2 "Zr is likely to be Zr(II) like" despite the FOS of Zr(IV). 4 In ref 1., we directly analyzed valence electron densities to ascertain that one electron charge resides on Ti in TiO 2 molecules and solids within less than half of the Ti−O bond length, independently of definitions of common charge assignment schemes. Specifically, valence densities around Ti in TiO 2 were compared to those in Ti 0 ...Ti 4+ ions. Such ions are directly detectable in plasma, 5,6 as opposed to, for example, XPS on solids (often cited as evidence for Ti 4+ ) where changes in charge surrounding the ionic core are detected indirectly. We confirmed that Bader charges provide a reasonable partitioning of space and Bader charges on the order of +2.5 |e| were most reasonable. We note that Bader charges do show full oxidation where it is known to happen (e.g., alkali atoms in semiconductors). 7−9 We also note that there is decent agreement between charge densities around Ti in a TiO 6 environment measured by X-ray/electron diffraction and computed by DFT. 10,11 Phillips fractional ionicity (based on Pauling electronegativity) of a Ti−O bond is 0.6, which implies a significant covalent character (compared, e.g., to 0.9 for LiF). Recent ionic potential models 12 that are able to reproduce properties of various TiO 2 polymorphs use charges of +2.4 and −1.2 |e| on Ti and O, respectively. 13 (Reference 13 reported structures and elastic properties of rutile TiO 2 , while we confirmed that a potential using these charges can reproduce structures of anatase, rutile, and bronze TiO 2 .) The "Ti 4+ " language implies no further oxidation of Ti and no further reduction of O. However, a degree of oxygen reduction is easily seen in ab initio calculations of doped oxides including TiO 2 , 7,14 and oxygen redox has finally been embraced in such systems. 15 That it took so long to recognize it 15 may have to do with the ubiquitous use of FOS to rationalize the mechanism. Given the above, "Ti 4+ " following from the ideology of FOS 16 appears to be a rather unphysical description. The FOS concept, which itself relies on the ionic approximation 17 that clearly does not hold in TiO 2 , predates modern quantum chemistry 18 and the knowledge gained from it, does not seem to be useful here. 19 ■ AUTHOR INFORMATION

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Effect of light gas atom inclusions on the characteristics of laser-produced plasma ions

Cited by 3 publications

References 14 publications

Density-Based Descriptors of Redox Reactions Involving Transition Metal Compounds as a Reality-Anchored Framework: A Perspective

Density-Based Descriptors of Redox Reactions Involving Transition Metal Compounds as a Reality-Anchored Framework: A Perspective

Density-based Descriptors of Redox Reactions Involving Transition Metal Compounds as a Reality-anchored Framework: A Perspective

Addition to “On the Charge State of Titanium in Titanium Dioxide”

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