First-Principles Investigation of the Stability of the Oxygen Framework of Li-Rich Battery Cathodes

ABSTRACTLithium-rich layered oxides such as Li2MnO3 have shown great potential as cathodes in Li-ion batteries, mainly because of their large capacities. However, these materials still suffer from structural degradation as the battery is cycled, reducing the average voltage and capacity of the cell. The voltage fade is believed to be related to the migration of transition metals into the lithium layer, linked to the formation of O-O dimers with a short bond length, which in turn is driven by the presence of oxygen holes due to the participation of oxygen in the redox process. We investigate the formation of O-O dimers for partially charged O1-Li2MnO3 using a first-principles density functional theory approach by calculating the reaction energy and kinetic barriers for dimer formation. Next, we perform similar calculations for partially charged O1-Li2IrO3, a Li-rich material for which the voltage fade was not observed during cycling. When we compare the stability of the oxygen framework, we conclude that the formation of O-O dimers is both thermodynamically and kinetically viable for O1-Li0.5MnO3. For O1-Li0.5IrO3, we observe that the oxygen lattice is much more stable, either returning to its original state when perturbed, or resulting in a structure with an O-O dimer that is much higher in energy. This can be explained by the mixed redox process for Li2IrO3, which is also shown from the calculated magnetic moments. The lack of O-O dimer formation in O1-Li0.5IrO3 provides valuable insight as to why Li2IrO3 does not demonstrate a voltage fade as the battery is cycled, which can be used to design Li-rich battery cathodes with an improved cycling performance.

Download Full-text

Ferromagnetic Half-Metal Cyanamides Cr(NCN)2 Predicted from First Principles Investigation

Materials ◽

10.3390/ma13081805 ◽

2020 ◽

Vol 13 (8) ◽

pp. 1805

Author(s):

Zhilue Wang ◽

Shoujiang Qu ◽

Hongping Xiang ◽

Zhangzhen He ◽

Jun Shen

Keyword(s):

First Principles ◽

Electronic Structures ◽

Density Functional ◽

Magnetic Moments ◽

Electronic Correlation ◽

Functional Theory ◽

Half Metal ◽

Equivalent Site ◽

Magnetic Couplings ◽

The Stability

The stability, physical properties, and electronic structures of Cr(NCN)2 were studied using density functional theory with explicit electronic correlation (GGA+U). The calculated results indicate that Cr(NCN)2 is a ferromagnetic and half-metal, both thermodynamically and elastically stable. A comparative study on the electronic structures of Cr(NCN)2 and CrO2 shows that the Cr atoms in both compounds are in one crystallographically equivalent site, with an ideal 4+ valence state. In CrO2, the Cr atoms at the corner and center sites have different magnetic moments and orbital occupancies, moreover, there is a large difference between the intra- (12.1 meV) and inter-chain (31.2 meV) magnetic couplings, which is significantly weakened by C atoms in Cr(NCN)2.

Download Full-text

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

10.26434/chemrxiv.8052218.v3 ◽

2019 ◽

Author(s):

Henrik Pedersen ◽

Björn Alling ◽

Hans Högberg ◽

Annop Ektarawong

Keyword(s):

Thin Films ◽

Thermodynamic Stability ◽

First Principles ◽

Thermal Equilibrium ◽

Density Functional ◽

Van Der Waals ◽

Chemical Vapor ◽

First Principles Calculations ◽

Functional Theory ◽

The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

Download Full-text

Site preference and atomic ordering in the ternary Rh5Ga2As: first-principles calculations

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1515/zkri-2021-2019 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Nilanjan Roy ◽

Sucharita Giri ◽

Harshit ◽

Partha P. Jana

Keyword(s):

Total Energy ◽

First Principles ◽

Density Functional ◽

Structure Type ◽

Site Preference ◽

X Ray Diffraction ◽

Atomic Ordering ◽

Functional Theory ◽

The Stability ◽

Bonding Characteristics

Abstract The site preference and atomic ordering of the ternary Rh5Ga2As have been investigated using first-principles density functional theory (DFT). An interesting atomic ordering of two neighboring elements Ga and As reported in the structure of Rh5Ga2As by X-ray diffraction data only is confirmed by first-principles total-energy calculations. The previously reported experimental model with Ga/As ordering is indeed the most stable in the structure of Rh5Ga2As. The calculation detected that there is an obvious trend concerning the influence of the heteroatomic Rh–Ga/As contacts on the calculated total energy. Interestingly, the orderly distribution of As and Ga that is found in the binary GaAs (Zinc-blende structure type), retained to ternary Rh5Ga2As. The density of states (DOS) and Crystal Orbital Hamiltonian Population (COHP) are calculated to enlighten the stability and bonding characteristics in the structure of Rh5Ga2As. The bonding analysis also confirms that Rh–Ga/As short contacts are the major driving force towards the overall stability of the compound.

Download Full-text

The stability and electronic and photocatalytic properties of the ZnWO4 (010) surface determined from first-principles and thermodynamic calculations

RSC Advances ◽

10.1039/d1ra03218f ◽

2021 ◽

Vol 11 (38) ◽

pp. 23477-23490

Author(s):

Yonggang Wu ◽

Jihua Zhang ◽

Bingwei Long ◽

Hong Zhang

Keyword(s):

Phase Diagram ◽

Density Functional Theory ◽

First Principles ◽

Density Functional ◽

Thermodynamic Calculations ◽

Photocatalytic Properties ◽

Thermodynamic Approach ◽

Functional Theory ◽

Stability Phase Diagram ◽

The Stability

The ZnWO4 (010) surface termination stability is studied using a density functional theory-based thermodynamic approach. The stability phase diagram shows that O-Zn, DL-W, and DL-Zn terminations of ZnWO4 (010) can be stabilized.

Download Full-text

Magnetic Properties of Embedded Rh Clusters in Ni Matrix

MRS Proceedings ◽

10.1557/proc-384-535 ◽

1995 ◽

Vol 384 ◽

Author(s):

Zhi-Qiang Li ◽

Yuichi Hashi ◽

Jing-Zhi Yu ◽

Kaoru Ohno ◽

Yoshiyuki Kawazoe

Keyword(s):

Magnetic Properties ◽

Electronic Structure ◽

First Principles ◽

Density Functional ◽

Local Density ◽

Magnetic Moments ◽

Functional Formalism ◽

Rhodium Clusters ◽

Spin Polarized ◽

Local Density Functional

ABSTRACTThe electronic structure and magnetic properties of rhodium clusters with sizes of 1 - 43 atoms embedded in the nickel host are studied by the first-principles spin-polarized calculations within the local density functional formalism. Single Rh atom in Ni matrix is found to have magnetic moment of 0.45μB. Rh13 and Rhl 9 clusters in Ni matrix have lower magnetic moments compared with the free ones. The most interesting finding is tha.t Rh43 cluster, which is bulk-like nonmagnetic in vacuum, becomes ferromagnetic when embedded in the nickel host.

Download Full-text

Magnetism and Half-Metallicity in (100) Surface of Inverse Heusler Mn2CoSb

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1015.377 ◽

2014 ◽

Vol 1015 ◽

pp. 377-380

Author(s):

Tao Chen ◽

Ying Chen ◽

Yin Zhou ◽

Hong Chen

Keyword(s):

Density Functional Theory ◽

Magnetic Properties ◽

First Principles ◽

Heusler Alloy ◽

Density Functional ◽

Magnetic Moments ◽

Surface States ◽

First Principles Calculations ◽

Half Metallicity ◽

Functional Theory

Using the first-principles calculations within density functional theory (DFT), we investigated the electronic and magnetic properties of (100) surface of inverse Heusler alloy Mn2CoSb with five different terminations. Our work reveals that the surface Mn atom moves to vacuum while surface Co atom moves to slab. Moreover, duo to the reason that the surface atom lost half of the nearest atoms with respect to the bulk phase, resulting in the decrease of hybridization, the atom-resolved spin magnetic moments of surface atoms are enhanced. Further investigation on DOS and PDOS showed that half-metallicity was preserved only in SbSb-termination while was destroyed in MnCo-, MnSb-, MnMn-, and CoCo-termination due to the appearance of surface states.

Download Full-text

The tuning effect of the electric field on the physical properties of some typical wurtzite semiconductors

Modern Physics Letters B ◽

10.1142/s0217984917503109 ◽

2017 ◽

Vol 31 (33) ◽

pp. 1750310 ◽

Cited By ~ 1

Author(s):

Jia-Ning Li ◽

San-Lue Hu ◽

Hao-Yu Dong ◽

Xiao-Ying Xu ◽

Jia-Fu Wang ◽

...

Keyword(s):

Electric Field ◽

Physical Properties ◽

First Principles ◽

Electronic Structures ◽

Density Functional ◽

Great Influence ◽

Semiconductor Materials ◽

Functional Theory ◽

The Stability ◽

Wurtzite Semiconductors

Under the tuning of an external electric field, the variation of the geometric structures and the band gaps of the wurtzite semiconductors ZnS, ZnO, BeO, AlN, SiC and GaN have been investigated by the first-principles method based on density functional theory. The stability, density of states, band structures and the charge distribution have been analyzed under the electric field along (001) and (00[Formula: see text]) directions. Furthermore, the corresponding results have been compared without the electric field. According to our calculation, we find that the magnitude and the direction of the electric field have a great influence on the electronic structures of the wurtzite materials we mentioned above, which induce a phase transition from semiconductor to metal under a certain electric field. Therefore, we can regulate their physical properties of this type of semiconductor materials by tuning the magnitude and the direction of the electric field.

Download Full-text

The effect of Ru on Ti50Pd50 high temperature shape memory alloy: a first-principles study

MRS Advances ◽

10.1557/adv.2019.331 ◽

2019 ◽

Vol 4 (44-45) ◽

pp. 2419-2429 ◽

Cited By ~ 1

Author(s):

R. G. Diale ◽

R. Modiba ◽

P. E. Ngoepe ◽

H. R. Chauke

Keyword(s):

First Principles ◽

Density Functional ◽

Lattice Parameter ◽

Heat Of Formation ◽

Partial Substitution ◽

Martensitic Transformation Temperature ◽

Functional Theory ◽

Equilibrium Lattice Parameter ◽

Strengthening Element ◽

The Stability

ABSTRACTThe stability of the Ti50Pd50-xRux alloy was investigated using first-principles density functional theory within the plane-wave pseudopotential method. Firstly, the Ti50Pd50 gave equilibrium lattice parameter and lowest heats of formation in better agreement with experimental data to within 3%. The heat of formation decreases with an increase in Ru concentration, consistent with the trend of the density of states which is lowered at the Fermi level as Ru content is increased which suggests stability. It was also found that from the calculated elastic constants the structures showed positive shear modulus above 20 at. % Ru, condition of stability. Furthermore, the addition of Ru was found to strengthen the Ti50Pd50-xRux system at higher concentrations. The thermal coefficients of linear expansion for the Ti50Pd31.25Ru18. 75 are higher at low temperature, and that the TiPd-Ru system tends to expand more at low content of 18.75 at. % Ru than at higher content. Partial substitution of Pd with Ru was found more effective as a strengthening element and may enhance the martensitic transformation temperature of the Ti50Pd50 alloy.

Download Full-text

First-Principles Study of the Stabilization and Mechanical Properties of Rare-Earth Ferritic Perovskites (RFeO3, R = La, Eu, Gd)

Applied Sciences ◽

10.3390/app10114008 ◽

2020 ◽

Vol 10 (11) ◽

pp. 4008

Author(s):

Mahdi Faghihnasiri ◽

Vahid Najafi ◽

Farzaneh Shayeganfar ◽

Ali Ramazani

Keyword(s):

Mechanical Properties ◽

Rare Earth ◽

First Principles ◽

Density Functional ◽

Mechanical Response ◽

External Loading ◽

Chemical Bonds ◽

Functional Theory ◽

Density Values ◽

The Stability

Current research aims to investigate the mechanical properties of rare earth perovskite ferrites (RFeO3, R = La, Eu, Gd) utilizing density functional theory (DFT) calculations. Using the revised Perdew–Burke–Ernzerhof approximation for solids (PBEsol) approximation, the elastic constants, bulk, Young’s, and shear modulus, Poisson’s ratio, and anisotropic properties are calculated. The quantum theory of atoms in molecules (QTAIM) is employed to analyze the stability of chemical bonds in the structures subjected to an external loading. Based on these calculations, Fe-O and R-O bonds can be considered as nearly ionic, which is due to the large difference in electronegativity of R and Fe with O. Additionally, our results reveal that the charge density values of the Fe-O bonds in both structures remain largely outside of the ionic range. Finally, the mechanical response of LaFeO3, EuFeO3, and GdFeO3 compounds to various cubic strains is investigated. The results show that in RFeO3 by increasing the radius of the lanthanide atom, the mechanical properties of the material including Young’s and bulk modulus increase.

Download Full-text