Available online at www.sciencedirect.com International Journal of Hydrogen Energy 29 (2004) 497–500 www.elsevier.com/locate/ijhydene Density of states induced by a hydrogenic impurity in a metal S.A.Serebrinsky,J.L.Gervasoni ∗; 1 Centro At omico Bariloche and Instituto Balseiro, Comisi on Nacional de Energ a At omica and Univ. Nac. de Cuyo; (8400) S. C. de Bariloche, R o Negro, Argentina Accepted 7 February 2003 Abstract In this work, we present a parametrization of the density of states induced by a hydrogenic impurity in a metal that is describedbyajellium.Theparametrizationhasthemostimportantfeaturesoftheinduceddensityofstates(I-DOS).Among others, it includes the l = 0 shallow doubly occupied bound state observed at low jellium densities when rs is higher than the binding value rs; B, and is consistent with the charge pile-up around the hydrogen due to the non-linear screening. It also addresses the innite discontinuity in the l = 0 I-DOS at the bottom of the band when rs exceeds rs; B. Our results compare wellwithothercalculations,includingmoresophisticatedonesthatincludespin-polarizedandmany-bodycalculations.Many applications may take advantage of the tractability of this parametrization, as a reference or for specic calculations. ? 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. Keywords: Density of states; Hydrogen–metallic systems 1. Introduction The behavior of hydrogen in metallic systems has been the object of several experimental studies, such as heat of solution, diusion properties and interaction with defects [1]. From a theoretical point of view, a complete theory musttakeintoaccountthelocalnatureofstronginteractions with nearest neighbours as well as the extended nature of electronic states in the conduction band of the metal, and both behaviours must be taken into account together in a self-consistentway.Untilnow,theexistingnumericalcalcu- lationshaveemphasizedoneofthesetwoaspectsseparately [2–6]. The electronic structure of impurities in metals is an important problem in the theory of alloys because in many cases the linear response theory is inadequate. Induced density of states (I-DOS) is an example where non-linear screening is important. Band structure and cluster cal- culations have been developed to investigate particular ∗ Corresponding author. Tel.: +54-2944-445118; fax: +54- 2944-445299. E-mail address: gervason@cab.cnea.gov.ar (J.L. Gervasoni). 1 Also member of the Consejo Nacional de Investigaciones Cient casyT ecnicas (CONICET), Argentina. aspectsoftheelectronicstructureofpointdefectsinmetals [7–9]. In the present work, we study the impurity-induced den- sity of states (IDOS) g(), which can be used as a start- ing point for the understanding of the electronic aspects of impurities(H; D; T )inametal.Inordertoeasethecompre- hensionandhandlingoftheelectronicstructureinducedby impurities in metals, we propose parametrizing the change g in the density of single-particle states due to the impu- ritiesintermsofananalyticfunctionoftheenergy  = k 2 = 2 and the electron gas parameter rs =( 3 4 n0) 1=3 . In Section 2, we explain the method used for the calculation of g(k ), and in Section 3 we set up to the parametrization, while considering some physical aspects of g. In Section 4, we discuss the main features of the parametrization and comment on some perspectives for further progress. 2. Theoretical method Therststepistocomputetheself-consistentg forsev- eral rs valuesinthemetallicrange.Forthispurposeweuse the Kohn–Sham [10] scheme of the spin-independent den- sity functional theory [11]. The procedure closely follows 0360-3199/$30.00 ? 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/S0360-3199(03)00093-4