Cavities and Channels in Electrides

Dye, James; Wagner, Michael J.; Overney, G.; Huang, Rui; Nagy, Tibor F.; Tománek, David

doi:10.1021/ja960548z

Cited by 97 publications

(107 citation statements)

References 42 publications

Supporting

Mentioning

102

Contrasting

Order By: Relevance

“…10,11,21,[35][36][37][38][39][40][41][42] Classical electrides are complex organic and, as a rule, non-metallic compounds in which some electrons occupy interstitial regions or cavities rather than residing on the alkali-metal nucleus or near them. [43][44][45][46] Neaton and Ashcroft 21 were the first to show that this type of localization can be induced in elemental metals under pressure. Using firstprinciples pseudopotential calculations, they predicted that above 100 GPa, Li adopts a semimetallic low-coordinated "paired" Cmca-4 phase with charge density peaking in the interstitial regions, loosely analogous to organic electrides.…”

Section: Introductionmentioning

confidence: 99%

Chemical bonding in hydrogen and lithium under pressure

Naumov

Hemley

Hoffmann

et al. 2015

The Journal of Chemical Physics

View full text Add to dashboard Cite

Though hydrogen and lithium have been assigned a common column of the periodic table, their crystalline states under common conditions are drastically different: the former at temperatures where it is crystalline is a molecular insulator, whereas the latter is a metal that takes on simple structures. On compression, however, the two come to share some structural and other similarities associated with the insulator-to-metal and metal-to-insulator transitions, respectively. To gain a deeper understanding of differences and parallels in the behaviors of compressed hydrogen and lithium, we performed an ab initio comparative study of these systems in selected identical structures. Both elements undergo a continuous pressure-induced s-p electronic transition, though this is at a much earlier stage of development for H. The valence charge density accumulates in interstitial regions in Li but not in H in structures examined over the same range of compression. Moreover, the valence charge density distributions or electron localization functions for the same arrangement of atoms mirror each other as one proceeds from one element to the other. Application of the virial theorem shows that the kinetic and potential energies jump across the first-order phase transitions in H and Li are opposite in sign because of non-local effects in the Li pseudopotential. Finally, the common tendency of compressed H and Li to adopt three-fold coordinated structures as found is explained by the fact that such structures are capable of yielding a profound pseudogap in the electronic densities of states at the Fermi level, thereby reducing the kinetic energy. These results have implications for the phase diagrams of these elements and also for the search for new structures with novel properties.

show abstract

Section: Introductionmentioning

confidence: 99%

Chemical bonding in hydrogen and lithium under pressure

Naumov

Hemley

Hoffmann

et al. 2015

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…A first step of such characterizations would be visualizing the cavities and channels which are expected to confine anionic electrons. This can be simply realized by plotting isosurfaces constructed from a sum of the molecular van der Waals surfaces . Alternatively, crystal voids can be visualized by plotting the procrystal density defined as the sum of spherically averaged atomic electron densities for all atoms belonging to the crystal .…”

Section: Computational Characterizationmentioning

confidence: 99%

Electride: from computational characterization to theoretical design

Zhao

Kan

2016

WIREs Comput Mol Sci

View full text Add to dashboard Cite

Electrides are a class of materials in which anionic electrons are spatially separated from the positively charged crystalline framework. With such a unique structure, electrides show great potential in various applications, such as superconductivity, electronics, and catalysis. A number of organic and inorganic electrides have been successfully synthesized in experiment, and their novel electronic structures are studied both computationally and experimentally. Computational characterization can provide information which is difficult to be obtained from experiment. In electronic structure calculations, charge density, noncovalent interaction (NCI) index, electron localization function (ELF), and electrostatic potential (ESP) can be analyzed to identify anionic electrons in confined space. On the other hand, theoretical studies can also be used to design new electrides, such as in a recent instance of two-dimensional (2D) electride screening. Alternatively, new applications and novel electron systems based on electrides can be explored theoretically. As an example, based on Ca 2 N electride, an intrinsic 2D electron gas system in free space (2DEG-FS) has been proposed. With the aid of computational characterization and theoretical design, electride study will continue to be an important field in materials science.

show abstract

“…Equations (16) and (17) imply thatL z commutes withĤ . Thus, a solution of the Schrödinger equation,…”

Section: B Two-electron Hamiltonianmentioning

confidence: 99%

“…This system is relevant to discussions of semiconductor quantum dots of cylindrical shape, confined electrons in the presence of external fields, and so-called Wigner molecules, as well as plainly for aesthetic reasons. Our principal motivation for attacking this problem, however, has to do with an interesting class of materials called electrides-ionic solids in which electrons localized in irregularly shaped and interconnected cavities act as anions [16][17][18]. Our long-term objective is to develop a general method for studying electrons in networks of cavities and channels of complex shapes that are found in actual electrides.…”

Section: Introductionmentioning

confidence: 99%

Two electrons in a cylindrical box: An exact configuration-interaction solution

Ryabinkin

Staroverov

2010

Phys. Rev. A

View full text Add to dashboard Cite

The problem of two Coulombically interacting electrons confined in a cylindrical potential box with impenetrable walls is solved by the method of full configuration interaction (CI) for states with zero axial component of the total orbital angular momentum, including the ground state 1 + g . The number of variables in the Schrödinger equation is reduced from six to five by separating theL z operator from the complete Hamiltonian. Two-electron basis sets of symmetry-adapted configuration state functions are constructed from real eigenfunctions of the one-electron Hamiltonian for a cylindrical potential box. Kinetic energy integrals are evaluated analytically. Electron repulsion integrals are computed by developing a separable expression for the 1/r 12 operator in the form of a double Fourier-Bessel-Fourier-cosine series and using enough terms to achieve a relative accuracy of 10 −10 for the eigenvalues. Energy-level ordering and electron densities of selected electronic states are reported for cylindrical cavities of varying size with a fixed 1:1 length-to-diameter ratio. A remarkable feature of this system is that convergence of the full CI energy with respect to the one-electron basis set varies dramatically with the extent of confinement: For small cavities, the rate of approaching the basis-set limit is similar to that for two-electron atoms but is significantly faster for large cavities. Formation of singlet and triplet Wigner molecules is observed in cylindrical cavities with radii greater than about 5 bohrs.

show abstract

Cavities and Channels in Electrides

Cited by 97 publications

References 42 publications

Chemical bonding in hydrogen and lithium under pressure

Chemical bonding in hydrogen and lithium under pressure

Electride: from computational characterization to theoretical design

Two electrons in a cylindrical box: An exact configuration-interaction solution

Contact Info

Product

Resources

About