Chen’s lattice inversion embedded-atom method for Ni-Al alloy

The structural properties, the enthalpies of formation, and the mechanical properties of some Ni-Al intermetallic compounds （NiAl, Ni3Al, NiAl3, Ni5Al3, Ni3Al4） are studied by using Chen＇s lattice inversion embedded-atom method （CLI-EAM）. Our calculated lattice parameters and cohesive energies of Ni-A1 compounds are consistent with the experimental and the other EAM results. The results of enthalpy of formation indicate a strong chemical interaction between Ni and Al in the intermetallic compounds. Through analyzing the alloy elastic constants, we find that all the Ni-Al intermetallic compounds discussed are mechanically stable. The bulk moduli of the compounds increase with the increasing Ni concentration. Our results also suggest that NiAl, Ni3Al, NiAl3, and Ni5Al3 are ductile materials with lower ratios of shear modulus to bulk modulus; while Ni3Al4 is brittle with a higher ratio.

Construction of embedded-atom-method interatomic potentials for alkaline metals (Li,Na,and K) by lattice inversion

The lattice-inversion embedded-atom-method interatomic potential developed previously by us is extended to alkaline metals including Li,Na,and K.It is found that considering interatomic interactions between neighboring atoms of an appropriate distance is a matter of great significance in constructing accurate embedded-atom-method interatomic potentials,especially for the prediction of surface energy.The lattice-inversion embedded-atom-method interatomic potentials for Li,Na,and K are successfully constructed by taking the fourth-neighbor atoms into consideration.These angular-independent potentials markedly promote the accuracy of predicted surface energies,which agree well with experimental results.In addition,the predicted structural stability,elastic constants,formation and migration energies of vacancy,and activation energy of vacancy diffusion are in good agreement with available experimental data and first-principles calculations,and the equilibrium condition is satisfied.

Atomistic simulation of site preference,Curie temperature,and lattice vibration of Nd_2Co_(7-x)Fe_x

The effects of Fe substitution for Co on the structural stability and the site preference of intermetallics Nd2CoT-xFex with a hexagonal Ce2NiT-type structure are studied by using a series of interatomic pair potentials. In Nd2CoT-xFex, Fe atoms are substituted for Co atoms with a strong preference for the 6h sites and the order of site preference is 6h, 4e, 4f, 2a, and 12k. Calculated lattice parameters are found to be consistent with the reported results in the literature. The variation behaviour of the Curie temperature of Nd2CoT-xFex is explained qualitatively by the exchange interaction model. The properties related to lattice vibration, such as phonon density of states and Debye temperature, are first evaluated for the Nd2Co7 xFex compounds.

The influence of 3d-metal alloy additions on the elastic and thermodynamic properties of CuPd_3

Embedded-atom method （EAM） potentials are used to investigate the effects of alloying （e.g. 3d-metals） on the trends of elastic and thermodynamic properties for CuPd3 alloy. Our calculated lattice parameter, cohesive energy, and elastic constants of CuPd3 are consistent with the available experimental and theoretical data. The results of elastic constants indicate that all these alloys are mechanically stable. Further mechanical behavior analysis shows that the additions of Cr, Fe, Co, and Ni could improve the hardness of CuPd3 while V could well increase its ductility. Moreover, in order to evaluate the thermodynamic contribution of 3d-metals, the Debye temperature, phonon density of states, and vibrational entropy for CuMPd6 alloy are also investigated.

Site preference and thermodynamic properties of R_3Ni_(13-x)Co_xB_2(R=Y,Nd and Sm)

This paper investigates the structural stability of intermetallics R3Ni13-xCoxB2 （R=Y, Nd and Sm） with Nd3Ni13B2-type structure and the site preferences of the transition element Co by using a series of interatomic pair potentials. The space group remains unchanged upon substitution of Co for Ni in R3Ni13-xCoxB2 and the calculated lattice constants are found to agree with reports in literatures. The calculated cohesive energy curves show that Co atoms substitute for Ni with a strong preference for the 3g sites and the order of site preference is 3g, 4h and 6i. Moreover, the total and partial phonon densities of states are first evaluated for the R3Ni13B2 compounds with the hexagonal Nd3Nil3B2-type structure.

Structure and Curie temperature of Y_2Fe_(17-x)Cr_x

The structures of Y2Fe17-xCrx are simulated by the ab initio potentials. The site preference of Cr atom in Y2Fe17 is evaluated and the order is determined as 4f, 12j, which is close to the experimental result. Based on the site preference behavior, the calculated parameters and the atom sites of Y-Fe-Cr system are studied. The result corresponds well to observed data. Further, the DOS of the relaxed structures are calculated and the variation in Curie temperature is explained qualitatively by the spin-fluctuation theory.

Flexible atomic buckling and homogeneous edge states in few-layer Bi(110)films

The structure and edge states of two-dimensional few-layer Bi(110)films grown on a graphene/SiC substrate were studied by low-temperature scanning tunneling microscopy and spectroscopy.We found that the local density of states of few-layer Bi(110)films are layer-dependent and that the films transition from exhibiting semiconducting characteristics to metallic ones as the number of layers increases.The in-plane lattice structure has numerous displacements and inversions,which implies that the atomic arrangement and atomic buckling in ultrathin Bi(110)films are flexible.The edges formed between 4-monolayer Bi(110)and graphene are reconstructed and distorted,and the corresponding edge states are topographically dependent.Steps from the substrate and domain boundaries also modify the electronic structures and induce additional defect-dependent states.We also found that the zigzag-shaped step edges in few-layer Bi(110)films are nonreconstructed and possess layer-dependent homogeneous edge states,providing a very likely platform for further research on quantum interference of the edge mode in order to confirm the topology in Bi(110).