Next Article in Journal
Quantum Crystallography in the Last Decade: Developments and Outlooks
Previous Article in Journal
Crystal Structure and Hirshfeld Surface Analysis of Bis(Triethanolamine)Nickel(II) Dinitrate Complex and a Revelation of Its Characteristics via Spectroscopic, Electrochemical and DFT Studies Towards a Promising Precursor for Metal Oxides Synthesis
Previous Article in Special Issue
Revisiting the Zintl‒Klemm Concept for ALn2Ag3Te5-Type Alkaline-Metal (A) Lanthanide (Ln) Silver Tellurides
Open AccessArticle

On the New Oxyarsenides Eu5Zn2As5O and Eu5Cd2As5O

1
Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA
2
The Charter School of Wilmington, Wilmington, DE 19807, USA
*
Authors to whom correspondence should be addressed.
Crystals 2020, 10(6), 475; https://doi.org/10.3390/cryst10060475
Received: 20 May 2020 / Revised: 28 May 2020 / Accepted: 1 June 2020 / Published: 3 June 2020
(This article belongs to the Special Issue Compounds with Polar Metallic Bonding Volume II)
The new quaternary phases Eu5Zn2As5O and Eu5Cd2As5O have been synthesized by metal flux reactions and their structures have been established through single-crystal X-ray diffraction. Both compounds crystallize in the centrosymmetric space group Cmcm (No. 63, Z = 4; Pearson symbol oC52), with unit cell parameters a = 4.3457(11) Å, b = 20.897(5) Å, c = 13.571(3) Å; and a = 4.4597(9) Å, b = 21.112(4) Å, c = 13.848(3) Å, for Eu5Zn2As5O and Eu5Cd2As5O, respectively. The crystal structures include one-dimensional double-strands of corner-shared MAs4 tetrahedra (M = Zn, Cd) and As–As bonds that connect the tetrahedra to form pentagonal channels. Four of the five Eu atoms fill the space between the pentagonal channels and one Eu atom is contained within the channels. An isolated oxide anion O2– is located in a tetrahedral hole formed by four Eu cations. Applying the valence rules and the Zintl concept to rationalize the chemical bonding in Eu5M2As5O (M = Zn, Cd) reveals that the valence electrons can be counted as follows: 5 × [Eu2+] + 2 × [M2+] + 3 × [As3–] + 2 × [As2–] + O2–, which suggests an electron-deficient configuration. The presumed h+ hole is confirmed by electronic band structure calculations, where a fully optimized bonding will be attained if an additional valence electron is added to move the Fermi level up to a narrow band gap (Eu5Zn2As5O) or pseudo-gap (Eu5Cd2As5O). In order to achieve such a formal charge balance, and hence, narrow-gap semiconducting behavior in Eu5M2As5O (M = Zn, Cd), europium is theorized to be in a mixed-valent Eu2+/ Eu3+ state. View Full-Text
Keywords: oxypnictide; Zintl phases; europium; mixed valence; zinc; arsenic; oxygen oxypnictide; Zintl phases; europium; mixed valence; zinc; arsenic; oxygen
Show Figures

Graphical abstract

MDPI and ACS Style

Darone, G.M.; Baranets, S.A.; Bobev, S. On the New Oxyarsenides Eu5Zn2As5O and Eu5Cd2As5O. Crystals 2020, 10, 475.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Search more from Scilit
 
Search
Back to TopTop