LOGO Computational prediction on the interface structure of SiC(SiO 2 )-Cu(Cu 2 O) composites from first principles Adviser: Ray Zhang （ professor ） Graduate student: Ruiyu Liu

LOGO Properties of SiC/Cu composites  Enhanced mechanical  Thermal  Electrical properties  The wetting and bonding between SiC and Cu was the most concern in the preparation of SiC/Cu composites.

LOGO Reason of using computer simulations It is very poor of wettability between copper and SiC. (R. Warren) To address these issues, it is important to achieve an understanding of the atomic structure at the SiC/Cu interface. 1. Which interface is the favorite one? 2. Which factors should be weakened, and which factors should be enhanced?

LOGO Previous work In the SiC/Cu coating particles, the surface of the SiC particles is covered by a film of SiO 2 because of the oxidation in air. SiC(100)-SiO 2 interface

LOGO Previous work  The surface of Cu crystallites are also covered by Cu 2 O, formed because of the oxidation of copper crystallites by the dissolved air in the aqueous solution during the coating process Cu (001)-Cu 2 O(001) interface

LOGO SiC(100)-SiO 2 interface model generation  1. The SiC(100) substrate modeled constraints a periodic 3×4 repeat unit.  2. Classical molecular dynamics were used to determine oxide structures which satisfy the imposed structural constraints, namely those deriving from the SiC substrate and from the periodic boundary conditions according to F. Devynck et al.  3. First principles calculations based on density functional theory (DFT) at level of the generalized gradient approximation were carried out.

LOGO Cu(100)-Cu 2 O interface model generation  Cu 2 O forms epitaxially with respect to the copper substrate where the relative orientation is (001) copper// (001) CuO 2 and [001] copper//CuO 2 and grows three-dimensionally to form oxide island according to our previous work.  The interface of Cu （ 001 ） /Cu 2 O （ 001 ） was built using Material Studio (MS).

LOGO Computational details  Five interface structure models between SiC(SiO 2 )-Cu(Cu 2 O) without any coordination defects were generated:  interface of SiC-Cu,  interface of SiC(SiO 2 )-Cu,  interface of SiC-Cu(Cu 2 O),  interface of SiC(SiO 2 )-Cu(Cu 2 O) (weak model)  interface of SiC(SiO 2 )-Cu(Cu 2 O) (strong model).

LOGO Computational details  First principles calculations were carried out by CASTEP, which employs the density functional theory plane-wave pseudopotential method.  The generalized gradient approximation Predew-Wang (PW91) exchange-correlation functional was employed.  The kinetic cutoff for the plane-wave expansion was set to 400 eV, and Monkhorst-Pack k-point mesh was set to 3×4×1.

LOGO Computational details  SiC-Cu interface SiC(SiO 2 )-Cu interface

LOGO Computational details  SiC-Cu(Cu 2 O) interface SiC(SiO 2 )-Cu(Cu 2 O) interface (weak model)

LOGO Computational details SiC(SiO 2 )-Cu(Cu 2 O) interface (strong model) The Cu 2 O layer is attached to the substrate through oxygen atoms bound to Cu atoms of the oxide film and to one Si atoms of the support.

LOGO Computational details  The table showed that the spacing between the adjacent slabs In the interface of SiC(SiO 2 )-Cu(Cu 2 O): InterfaceSiC-CuSiC(SiO 2 )-Cu Initial stage3.5Å Final stage3.2Å InterfaceSiC-Cu(Cu 2 O)SiC(SiO 2 )-Cu(Cu 2 O) (weak model) Initial stage3.6Å3.9Å Final stage2.9Å2.8Å

LOGO Total energy of each material  Binding energy of interface ( ) is equal to the energy of breaking interface bond and dividing one interface into tow free surfaces.

LOGO Total energy of each material MaterialsSiCCu Total energy E+003 eV E+00410eV MaterialsSiC(SiO 2 )Cu(Cu 2 O) Total energy E E+004 MaterialsSiC-CuSiC(SiO 2 )-Cu Total energy E E+004 MaterialsSiC-Cu(Cu 2 O)SiC(SiO 2 )-Cu(Cu 2 O) (weak model) Total energy E+004 MaterialsSiC(SiO 2 )-Cu(Cu 2 O) (strong model) Total energy

LOGO Binding energy of the five interface InterfaceSiC(SiO 2 )Cu(Cu 2 O) Binding energy InterfaceSiC-CuSiC(SiO 2 )-Cu Binding energy InterfaceSiC-Cu(Cu 2 O) Binding energy ev InterfaceSiC(SiO 2 )-Cu(Cu 2 O) (weak model) Binding energy InterfaceSiC(SiO 2 )-Cu(Cu 2 O) (strong model) Binding energy

LOGO 4. Unfinished conclusion 1. Binding energy Know which interface is the favorite one? 2. Density of State Know why through analyzing bonding properties.

LOGO THANK YOU ！ PLEASE GIVE YOUR PRECIOUS SUGGESTIONS ！