Influence of nickel(II) oxide surface magnetism on molecule adsorption: A first-principles study

The influence of the magnetism of transition metal oxide,nickel(II)oxide(NiO),on its surface reactivity and the dependence of surface reactivity on surface orientation and reactant magnetism were studied by density functional theory plus U calculations.We considered five different antiferromagnetically ordered structures and one ferromagnetically ordered structure,NiO(001)and Ni(011)surfaces,paramagnetic molecule NO,and nonparamagnetic molecule CO.The calculations showed that the dependence of surface energies on magnetism was modest,ranging from49to54meV/?2for NiO(001)and from162to172meV/?2for NiO(011).On NiO(001),both molecules preferred the top site of the Ni cation exclusively for all NiO magnetic structures considered,and calculated adsorption energies ranged from?0.33to?0.37eV for CO and from?0.42to?0.46eV for NO.On NiO(011),both molecules preferred the bridge site of two Ni cations irrespective of the NiO magnetism.It was found that rather than the long‐range magnetism of bulk NiO,the local magnetic order of two coordinated Ni cations binding to the adsorbed molecule had a pronounced influence on adsorption.The calculated NO adsorption energy at the(↑↓)bridge sites ranged from?0.99to?1.05eV,and become stronger at the(↑↑)bridge sites with values of?1.21to?1.30eV.For CO,although the calculated adsorption energies at the(↑↓)bridge sites(?0.73to?0.75eV)were very close to those at the(↑↑)bridge sites(?0.71to?0.72eV),their electron hybridizations were very different.The present work highlights the importance of the local magnetic order of transition metal oxides on molecular adsorption at multi‐fold sites.

Adsorption of 1,3,5-Triphenylbenzene Molecules and Growth of Graphene Nanoflakes on Cu(100)Surface

Adsorption of 1,3,5-triphenylbenzene （TPB） molecules on Cu（100） surface is studied using ultraviolet photo- electron spectroscopy （UPS） and density functional theory （DFT） calculations. Researches on the bottom-up fabrication of graphene nanoflakes （GNFs） with TPB as a precursor on the Cu（100） surface are carried out based on UPS and DFT calculations. Three emission features d, e and f originating from the TPB molecules are located at 3.095, 7.326 and 9.349 eV below the Fermi level, respectively. With the increase of TPB coverage on the Cu（100） substrate, the work function decreases due to the formation of interfacial dipoles and charge （electron） rearrangement at the TPB/Cu（100） interface. Upon the formation of GNFs, five emission characteristic peaks of g, h, i, j and k originating from the GNFs are located at 1.100, 3.529, 6.984, 8.465 and 9.606eV below the Fermi level, respectively. Angle resolved ultraviolet photoelectron spectroscopy （ARUPS） and DFT calculations indicate that TPB molecules adopt a lying-down configuration with their molecular plane nearly parallel to the Cu（100） substrate at the monolayer stage. At the same time, the lying-down configuration for the GNFs on the Cu（100） surface is also unveiled by ARUPS and DFT calculations.

Adsorption Regularity and Characteristics of sp^3-Hybridized Gas Molecules on Anatase TiO_2(101) Surface

We report the anatase titanium dioxide （101） surface adsorption of sp3-hybridized gas molecules, including NH3, 1-12 0 and CH4, using first-principles plane-wave ultrasoft pseudopotential based on the density functional theory. The results show that it is much easier for a surface with oxygen vacancies to adsorb gas molecules than it is for a surface without oxygen vacancies. The main factor affecting adsorption stability and energy is the polarizability of molecules, and adsorption is induced by surface oxygen vacancies of the negatively charged center. The analyses of state densities and charge population show that charge transfer occurs at the molecule surface upon adsorption and that the number of transferred charge reduces in the order of N, 0 and C. Moreover, the adsorption method is chemical adsorption, and adsorption stability decreases in the order of NH3, tt2 0 and CH4. Analyses of absorption and reflectance spectra reveal that after absorbed CH4 and H2 O, compared with the surface with oxygen vacancy, the optical properties of materials surface, including its absorption coefficients and reflectivity index, have slight changes, however, absorption coefficient and reflectivity would greatly increase after NH3 adsorption. These findings illustrate that anatase titanium dioxide （101） surface is extremely sensitive to NH3.

Surface effects of adsorption-induced resonance analysis on micro/nanobeams via nonlocal elasticity

The governing differential equation of micro/nanbeams with atom/molecule adsorption is derived in the presence of surface effects using the nonlocal elasticity. The effects of the nonlocal parameter, the adsorption density, and the surface parameter on the resonant frequency of the micro/nanobeams are investigated. It is found that, in ad- dition to the nonlocal parameter and the surface parameter, the bending rigidity and the adsorption-induced mass exhibit different behaviors with the increase in the adsorption density depending on the adatom category and the substrate material.

Insights into the adsorption of water and oxygen on the cubic CsPbBr_(3)surfaces:A first-principles study

The degradation mechanism of the all-inorganic perovskite solar cells in the ambient environment remains unclear.In this paper,water and oxygen molecule adsorptions on the all-inorganic perovskite(CsPbBr_(3))surface are studied by density-functional theory calculations.In terms of the adsorption energy,the water molecules are more susceptible than the oxygen molecules to be adsorbed on the CsPbBr_(3)surface.The water molecules can be adsorbed on both the CsBr-and PbBr-terminated surfaces,but the oxygen molecules tend to be selectively adsorbed on the CsBr-terminated surface instead of the PbBr-terminated one due to the significant adsorption energy difference.While the adsorbed water molecules only contribute deep states,the oxygen molecules introduce interfacial states inside the bandgap of the perovskite,which would significantly impact the chemical and transport properties of the perovskite.Therefore,special attention should be paid to reduce the oxygen concentration in the environment during the device fabrication process so as to improve the stability and performance of the CsPbBr_(3)-based devices.

Efficiently Adsorbing CO Molecules Using Al_6Si Cluster

Based on the density functional theory with generalized gradient approximation, the stable geometrical structures of one or more CO molecules adsorbed on the Al6Si cluster are investigated and the corresponding adsorption energies are also calculated. It is found that the cluster Al6Si can adsorb six CO molecules. The thermal stability of the（CO）6@Al6Si complexes is examined using the atom centered density matrix propagation molecular dynamics calculations at 373 K. The results show that two isomers of Al6Si cluster can solidly adsorb six CO molecules, and the other isomer adsorbs four ones. Therefore, the Al6Si cluster is a promising candidate for eliminating CO effectively.