Embedded-cluster study of core-level binding energies of magnesium and alkali impurities at the surface of MgO

Birkenheuer, U.; Corà, Furio; Pisani, Cesare; Scorza, Erminia; Perego, G.

doi:10.1016/s0039-6028(96)01184-3

Cited by 12 publications

(12 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In particular, the PC technique has proved capable of providing useful information on simple defects in MgO. 22,33,34 Of particular relevance for the present investigation is our study of core holes in magnesium and in substitutional alkali ions ͑X:Mg; XϭLi,Na͒ in MgO. 34 The two studies are similar as regards the description of the host system, the comparison of bulk with surface defects, the choice of the embedded clusters, the techniques used for calculating the energy and the equilibrium geometry and for the treatment of the spin-polarized defects.…”

Section: Introductionmentioning

confidence: 99%

The oxygen vacancy at the surface and in bulk MgO: An embedded-cluster study

Scorza¹,

Birkenheuer²,

Pisani³

1997

The Journal of Chemical Physics

145

122

View full text Add to dashboard Cite

The oxygen vacancy in bulk MgO and at its ͑001͒ surface have been studied by means of the EMBED program which adopts an embedded-cluster approach in the frame of the Hartree-Fock ͑HF͒ approximation ͓Comp. Phys. Comm. 82, 139 ͑1994͒; 96, 152 ͑1996͔͒: A spin restricted ͑RHF͒ or unrestricted ͑UHF͒ method has been used according to whether the vacancy contains an even number ͑F and F 2ϩ centers͒ or an odd number ͑F ϩ center͒ of electrons. The semi-infinite crystal has been simulated with a three-layer slab. Particular attention has been given to the optimization of the basis functions which serve to describe the trapped electron͑s͒ in the vacancy. The correlation energy was estimated using second order Mo "ller-Plesset theory. The three electronic configurations have been studied by allowing for relaxation of all neighboring ions. For the paramagnetic center, spin density data are provided and discussed with reference to results from EPR experiments and molecular cluster calculations.

show abstract

Section: Introductionmentioning

confidence: 99%

The oxygen vacancy at the surface and in bulk MgO: An embedded-cluster study

Scorza¹,

Birkenheuer²,

Pisani³

1997

The Journal of Chemical Physics

145

122

View full text Add to dashboard Cite

show abstract

“…85,86 This is usually done by introducing chemical potentials µ ± which are added to the pole positions of the one-particle Green's function, i.e., A n ( k) + µ + and I n ( k) + µ − . The (fundamental) band gap is the smallest difference between the energies for removing an electron from and attaching an electron to an N particle system:…”

Section: 8283mentioning

confidence: 99%

Ab initioGreen’s function formalism for band structures

et al. 2005

View full text Add to dashboard Cite

Using the Green's function formalism, an ab initio theory for band structures of crystals is derived starting from the Hartree-Fock approximation. It is based on the algebraic diagrammatic construction scheme for the self-energy which is formulated for crystal orbitals (CO-ADC). In this approach, the poles of the Green's function are determined by solving a suitable Hermitian eigenvalue problem. The method is not only applicable to the outer valence and conduction bands, it is also stable for inner valence bands where strong electron correlations are effective. The key to the proposed scheme is to evaluate the self-energy in terms of Wannier orbitals before transforming it to a crystal momentum representation. Exploiting the fact that electron correlations are mainly local, one can truncate the lattice summations by an appropriate configuration selection scheme. This yields a flat configuration space; i.e., its size scales only linearly with the number of atoms per unit cell for large systems and, under certain conditions, the computational effort to determine band structures also scales linearly. As a first application of the new formalism, a lithium fluoride crystal has been chosen. A minimal basis set description is studied, and a satisfactory agreement with previous theoretical and experimental results for the fundamental band gap and the width of the F 2p valence band complex is obtained.

show abstract

“…Many EMBED studies have been devoted to this kind of problems: substitutional and interstitial carbon in silicon [72,80]; substitutional aluminium, interstitial alkali atoms and oxygen vacancy in α-quartz [81]; substitutional aluminium in hexagonal BN [18]; substitutional sodium and Schottky pairs in LiF [82]; various defects in MgO: cationic [87] and anionic [83] vacancy, divacancy [82], substitutional alkali ions [88]; substitutional KOH and NaOH in proton-ordered ice structures [89]. These defects are often characterized by high point symmetry, which makes their study easier, because symmetry is thoroughly exploited in EMBED [22].…”

Section: Chemical Impurities and Vacancies In Semiconductors Insulatmentioning

confidence: 99%

“…This is perhaps one of the most promising areas for use of this code. A few applications can be cited: paramagnetic centers in ionic systems, where the calculated spin density can be compared with that resulting from electron spin resonance experiments [25,82,83,95]; core holes, and comparison of their formation energy with that resulting from ESCA experiments [88]; simulation of singlet-triplet transitions following ultraviolet irradiation, which are at the origin of interesting phenomena in catalytic problems [95] and in the creation of extended defects in optical fibers [85].…”

Section: Paramagnetic Defects and Local Excitationsmentioning

confidence: 99%

CRYSTAL and EMBED, two computational tools for the ab initio study of electronic properties of crystals

Pisani

Dovesi

Roetti

et al. 2000

Int. J. Quant. Chem.

Self Cite

View full text Add to dashboard Cite

ABSTRACT:The present study discusses the main features of the two programs CRYSTAL and EMBED developed for the ab initio study of the electronic properties of perfect periodic structures and of crystals with local defects, respectively. After a brief historical introduction, the structure of CRYSTAL is outlined and some specific aspects are discussed in detail: the use of local basis functions, the way of dealing with the Coulomb and the exchange series, the exploitation of point symmetry, the possibility to adopt either the Hartree-Fock approach or one among a variety of Kohn-Sham Hamiltonians. The present capabilities of the program are illustrated by a survey of selected applications from existing literature. Information is provided concerning work in progress aimed at removing some of the limitations of the code and improving its performance. The characteristics of EMBED are analyzed with emphasis given to the critical aspects of the method: limits of validity of the fundamental approximation on which the embedding technique relies, problems of convergence of the self-consistent procedure; and the delicate issue of the estimate of the defect formation energy. Again, a critical survey of applications clarifies the capabilities of the code. The envisaged improvements to be introduced in a forthcoming release of EMBED are presented. The present and prospective role of the two programs in the field of computational studies of condensed matter problems is outlined.

show abstract

Embedded-cluster study of core-level binding energies of magnesium and alkali impurities at the surface of MgO

Cited by 12 publications

References 18 publications

The oxygen vacancy at the surface and in bulk MgO: An embedded-cluster study

The oxygen vacancy at the surface and in bulk MgO: An embedded-cluster study

Ab initioGreen’s function formalism for band structures

CRYSTAL and EMBED, two computational tools for the ab initio study of electronic properties of crystals

Contact Info

Product

Resources

About