Study of structural and magnetic properties of Fe(80)P-9B(11) amorphous alloy by ab initio molecular dynamic simulation

The structural and magnetic properties of Fe80P9B11 amorphous alloy are investigated through ab initio molecular dynamic simulation. The structure evolution of Fe（80）P9B（11） amorphous alloy can be described in the framework of topological fluctuation theory, and the fluctuation of atomic hydrostatic stress gradually decreases upon cooling. The left sub peak of the second peak of Fe–B partial pair distribution functions（PDFs） becomes pronounced below the glass transition temperature, which may be the major reason why B promotes the glass formation ability significantly. The magnetization mainly originates from Fe 3d states, while small contribution results from metalloid elements P and B. This work may be helpful for developing Fe-based metallic glasses with both high saturation flux density and glass formation ability.

Structural Origins for Enhanced Thermal Stability and Glass‑Forming Ability of Co–B Metallic Glasses with Y and Nb Addition

The effects of Y and Nb addition on thermal stability,glass-forming ability(GFA),and magnetic softness of Co75B25 metallic glass(MG)were comprehensively investigated.The experimental results indicated that the thermal stability,GFA,and magnetic softness of the studied MGs increase in the order Co_(75)B_(25)<Co_(73)Nb_(2)B_(25)<Co_(71.5)Y_(3.5)B_(25)<Co_(69.5)Y_(3.5)Nb_(2)B_(25).The structural origins of the improved properties were revealed by ab initio molecular dynamics(AIMD)simulations and density functional theory(DFT)calculations.Results showed that the B-centered prism units are the primary structure-forming units of the four MGs,connect through vertex-,edge-,and face-shared(VS,ES,and FS)atoms,and Co-centered units tend to connect with Co/B-centered units via the intercross-shared(IS)atoms.The addition of Y and Nb not only plays the role of connecting atoms but also enhances both bond strengths and the fractions of icosahedral-like units in increasing order Co_(75)B_(25)<Co_(73)Nb_(2)B_(25)<Co_(71.5)Y_(3.5)B_(25)<Co_(69.5)Y_(3.5)Nb_(2)B_(25),which is conducive to the enhancement of the structural stability,atomic packing density,and viscosity,thereby improving thermal stability and GFA.In addition,the improvement of structural stability and homogeneity leads to enhanced magnetic softness.

Single Iron-dimer Catalysts on MoS_(2) Nanosheet for Potential Nitrogen Activation

Electrocatalytic nitrogen reduction reaction(NRR)is a promising way to produce ammonia(NH_(3))at ambient temperature and pressure.Herein,we have constructed single Fe dimer catalysts on a molybdenum disulfide monolayer for potential nitrogen activation.By employing ab initio molecular dynamics simulations,it is suggested that a dual iron-single atom site can be dynamically formed,which exhibits the similar Fe-S-Fe structure as the nitrogenase.We further identify an iron dimer with a sulfur vacancy as the active center for realistic nitrogen activation by the free energy calculations since the bridged sulfur is easy to be released in the form of H_(2)S during the reduction process.It is shown that N_(2)mainly adsorbs on the Fe_(2)dimer at the sulfur vacancies in the pattern of side-on configuration,and the nitrogen reduction reaction is proceeded by an enzymatic mechanism.Charge analyses further show that the Fe_(2)dimer mainly works as an electron reservoir while MoS_(2)substrate with one sulfur vacancy acts as an inert carrier to stabilize the Fe_(2)dimer.Overall,our work provides important insights into how N_(2)molecules were adsorbed and activated on Fe_(2)-doped MoS_(2),and provides new ideas for the transformation of actual reaction sites during electrochemical reactions.