Surface strain effects on the adsorption and the diffusion of Au atoms on MgO(001) surfaces

Jeon, Junjin,Yu, Byung Deok,Hyun, Sangil 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol. No.

<P>The effects of surface strain on the adsorption and the diffusion properties of a Au adatom on MgO(001) surfaces are studied using first-principles electronic-structure calculations based on the density functional theory. The adsorption of Au on MgO(001) is found to become stronger with increasing surface strain. In addition, the adsorption site of Au changes from a site on top of a surface O atom of MgO(001) to a site near a surface O atom for tensile surface strains over +4 %. In the case of a tensile surface strain of +7 %, the adsorption energy changes from -0.87 eV for unstrained MgO(001) to -1.17 eV. The variation in the charge states of Au on MgO(001) with surface strain, based on a Bader charge analysis, is also presented. The Bader charges of Au are found to become more negative as the surface strain increases. For a tensile surface strain of +7 %, the Bader charge is -0.38 |e|, more negative than the value of -0.29 |e| for unstrained MgO(001). Contrary to the adsorption energies and the charge states of Au, the variation in the surface diffusion barriers of Au on MgO(001) is found to be very small, less than 0.03 eV.</P>

Interfacial Properties in Ultrathin MgO Films on TiN(001) Surfaces: Ab-initio Calculations

Junjin Jeon,유병덕,손알로이시우스 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.2

By using ab-initio electronic structure calculations based on the density functional theory, wesystematically investigated the interfacial properties of the MgO/TiN(001) system with increasingMgO film thickness from one to three monolayers (ML). Atomic geometries and adhesion characteristicsof the MgO/TiN(001) systems in the range of 1- to 3-ML MgO are presented. O-Ti and Mg-Nbonds were formed across the interfaces. Our calculated energetics indicate that the interfacial adhesionof the MgO films to the TiN substrates was stronger than that for the metal-oxide systemsof MgO/Ag(001) and MgO/Fe(001). An analysis of the electronic properties of the MgO/TiN(001)systems was also performed. Upon the adsorption of the MgO overlayers, the work function of theTiN(001) surface was found to exhibit a significant decrease due to the large interface dipole formedat the interface of this system. Very interestingly, the obtained work functions of 1.89–1.96 eV for1- to 3-ML MgO films on TiN(001) were lower than those for other metal-supported MgO films.

Atomistic Processes of Ni and Pd Atoms on MgO(001) Surfaces with Surface-functional Hydroxyl Groups: Ab-initio Calculations

Junjin Jeon,유병덕 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.4

By using ab-initio calculations based on the density functional theory, we systematically studiedthe adsorption and the diffusion properties of Ni and Pd (XM) atoms on hydroxylated MgO(001)[MgOhdr(001)] surfaces. The energetics of adsorption, binding, and diffusion are presented and comparedwith those of XM atoms on clean MgO(001). The calculated energetics showed considerablyenhanced adsorption of XM on MgOhdr(001) compared to that on MgO(001). The stronger bindingof XM and OH on MgO(001) indicated the favorable formation of XMOH complexes instead of XMdimers on the surface. In the case of surface diffusion, XMOH on MgO(001) was observed to diffusevia a hopping process over the surface hollow sites. The diffusion of XMOH on MgO(001) wasslightly faster than that of XM atoms. Compared to the surface diffusion of PtOH on MgO(001),the surface diffusion energy barriers were in the following order, PtOH (0.89 eV) > NiOH (0.71eV) > PdOH (0.43 eV). Therefore, the surface dynamics of Ni, Pd, and Pt on MgOhdr(001) driventhermally at temperatures relevant to the catalytic activities of metal clusters are expected to bedifferent. The electronic structures and the charge states of XMOH on MgO(001) were analyzedfurther and compared with those of XM on MgO(001).

Dynamics of Pd monomers and dimers adsorbed on the (001) surfaces of strongly correlated nickel oxides

Jeon, Junjin,Yu, Byung Deok Elsevier 2015 Current Applied Physics Vol.15 No.2

<P><B>Abstract</B></P> <P>The adsorption and diffusion of Pd monomers and dimers on the (001) surfaces of strongly correlated nickel oxides were investigated using density functional theory combined with the on-site Coulomb repulsion <I>U</I>. The results were compared with those of Pd on nonmagnetic MgO(001). For the Pd monomer, the most stable adsorption site was found to be near the surface O atom. The surface diffusion of the Pd monomer occurred by a hopping process over surface hollow sites. The diffusion energy barrier was 0.21?eV, which was lower than that for Pd on MgO(001). In the case of the Pd dimer, the smallest and stable cluster, the most stable adsorption structure had a flat geometry, with both Pd atoms sitting above the neighboring surface O atoms. The surface diffusion of the Pd dimer occurred by rotational and sliding processes, in contrast to that of the Pd dimer on MgO(001). The diffusion energy barriers ranged from 0.33 to 0.36?eV. The values for the surface diffusion of Pd dimers on NiO(001) were lower than those of Pd on MgO(001). This suggests that Pd dimers move more rapidly on NiO(001) than on MgO(001), and that the sintering of Pd clusters closely related to catalytic activities can occur more easily compared to that of Pd on MgO(001).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ab-initio calculations on effects of oxide supports on the dynamics of Pd monomers and dimers on NiO(001). </LI> <LI> The surface diffusion of Pd monomers occurred by a hopping process. </LI> <LI> The surface diffusion of Pd dimers occurred by rotational and sliding processes. </LI> <LI> The dynamic properties and the sintering of Pd on NiO(001) were compared with those of Pd on MgO(001). </LI> </UL> </P>

Surface Strain Effects on the Adsorption of Au Adatoms on MgO(001) Surfaces with Surface O Vacancies

Junjin Jeon,박진우,유병덕 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.9

By employing ab-initio total-energy and electronic-structure calculations based on the densityfunctional theory, we studied the effects of surface strain "s on the adsorption properties of a Au adatom on defective MgO(001) surfaces with surface oxygen vacancies (Fs centers). The formation energy of the Fs center on MgO(001) varied very slightly in the region of "s from 6% to 4% and monotonically decreased with the increase in "s, from 4% to +6%. As "s increased, the adsorption energy (EFs ads) of Au on the Fs center of strained MgO(001) monotonically decreased and, in particular, showed a much larger decrease in EFs ads for a tensile surface strain of "s > +4%. The surface strain dependence on the physical properties, such as the charge states, the spatial charge rearrangement, for Au on the Fs center of strained MgO(001) surfaces was also analyzed. These results provide important physical information on the effects of surface strain on the adsorption of Au on MgO(001) surfaces with Fs centers.

Surface Strain Effects on the Adsorption and the Diffusion of Au Atoms on MgO(001) Surfaces

Junjin Jeon,유병덕,Sangil Hyun 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.12

The effects of surface strain on the adsorption and the diffusion properties of a Au adatom on MgO(001) surfaces are studied using first-principles electronic-structure calculations based on the density functional theory. The adsorption of Au on MgO(001) is found to become stronger with increasing surface strain. In addition, the adsorption site of Au changes from a site on top of a surface O atom of MgO(001) to a site near a surface O atom for tensile surface strains over +4 %. In the case of a tensile surface strain of +7 %, the adsorption energy changes from −0.87 eV for unstrained MgO(001) to −1.17 eV. The variation in the charge states of Au on MgO(001) with surface strain, based on a Bader charge analysis, is also presented. The Bader charges of Au are found to become more negative as the surface strain increases. For a tensile surface strain of +7 %, the Bader charge is −0.38 |e|, more negative than the value of −0.29 |e| for unstrained MgO(001). Contrary to the adsorption energies and the charge states of Au, the variation in the surface diffusion barriers of Au on MgO(001) is found to be very small, less than 0.03 eV.

First-principles Study of the Physical Properties of Ultrathin MgO Films on Fe(001) Surfaces

Junjin Jeon,유병덕 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.3

The physical properties of ultrathin MgO films supported on Fe(001) surfaces were systematically studied with increasing MgO thickness from one to three layers (L) by using a first-principles totalenergy approach based on the density functional theory. The atomic geometry and the adhesion characteristics of the metal-oxide interfaces of MgO/Fe(001) in the range of 1L ?3L MgO were investigated. O-Fe bonds were formed across the interfaces, and weak interfacial adhesion was observed. For each oxide thickness, the adhesion energy had an intermediate value between those for MgO/Ag(001) and MgO/Mo(001). The variations in the electronic structures of the Fe substrate and of the adsorbed MgO layers with MgO thickness are also presented. The shapes of the layerprojected densities of states exhibited significantly different features for the ultrathin MgO films. Changes in the work function of the Fe(001) surface upon the adsorption of ultrathin MgO films were investigated. The adsorption of ultrathin MgO films was found to decrease the work function by as much as 1.43 - 1.74 eV due to the positive interface dipole induced by the formation of the metal-oxide interface.

<i>Ab initio</i>study of incorporation ofO2molecules intoSi(001)surfaces: Oxidation bySiejection

Yu, B. D.,Kim, Young Jin,Jeon, Junjin,Kim, Hanchul,Yeom, H. W.,Lyo, I. W.,Kong, Ki-jeong,Miyamoto, Y.,Sugino, O.,Ohno, T. American Physical Society 2004 Physical review. B, Condensed matter and materials Vol.70 No.3