Structural, magnetic, electronic, and elastic properties of face-centered cubic PuH_x (x= 2, 3):GGA (LSDA) + U + SO

We perform first-principles calculations to investigate the structural, magnetic, electronic, and mechanical properties of face-centered cubic （fcc） Pull2 and fcc Pull3 using the full potential linearized augmented plane wave method （FP- LAPW） with the generalized gradient approximation （GGA） and the local spin density approximation （LSDA） taking account of both relativistic and strong correlation effects. The optimized lattice constant a0 = 5.371 A for fcc Pull2 and a0 = 5.343 A for fcc PuH3 calculated in the GGA ＋ sp （spin polarization） ＋ U （Hubbard parameter） ＋ SO （spin-orbit coupling） scheme are in good agreement with the experimental data. The ground state of fcc PuH3 is found to be slightly ferromagnetic. Our results indicate that fcc PuH2 is a metal while fcc PuH3 is a semiconductor with a band gap about 0.35 eV. We note that the SO and the strong correlation between localized Pu 5f electrons are responsible for the band gap of fcc PuH3. The bonds for PuH2 have mainly covalent character while there are covalent bonds in addition to apparent ionicity bonds for PuH3. We also predict the elastic constants of fcc PuH2 and fcc PuH3, which were not observed in the previous experiments.

Polishing of Titanium Alloy Blade Root with Elastic Magnetic Toolic Tool

Removal of milling marks at the root fillet of titanium alloy blade is a tough work because of the interference between the polishing tool and the workpiece.A polishing method based on elastic magnetic tool was proposed.The software ANSYS Maxwell was used to simulate the effect of different pole orientation arrangements on the magnetic field distribution.A comparison of polishing effect was made between elastic and inelastic magnetic pole carriers.The processing parameters of the elastic magnetic tool polishing for the blade root were optimized by orthogonal experiment(Taguchi)method.Results show that compared with the inelastic magnetic polishing tool,the elastic magnetic polishing tool with polyurethane as the pole carrier can effectively improve the surface quality of the polished workpiece.Under the optimal processing parameters(rotational speed=900 r/min,feeding rate=6 mm/min,machining gap=1.5 mm and abrasive size=10‒14μm),the original milling marks at the blade root are effectively removed and the average surface roughness Ra is dropped from 0.95μm to 0.12μm,which verifies the feasibility of the elastic magnetic polishing tool in the surface finishing of the titanium alloy blade root.

First principles study of structural, electronic, elastic and magnetic properties of cerium and praseodymium hydrogen system REH_x(RE:Ce, Pr and x=2, 3)

The structural, electronic, elastic and magnetic properties of cerium, praseodymium and their hydrides REH x（RE=Ce, Pr and x=2, 3） were investigated by the first principles calculations based on density functional theory using the Vienna ab-initio simulation package. At zero pressure all the hydrides were stable in the ferromagnetic state. The calculated lattice parameters were in good agreement with the experimental results. The bulk modulus decreased with the increase in the hydrogen content for these hydrides. The electronic structure revealed that di-hydrides were metallic whereas trihydrides were half metallic at zero pressure. A pressure-induced structural phase transition from cubic to hexagonal phase was predicted in these hydrides. The computed elastic constants indicated that these hydrides were mechanically stable at zero pressure. The calculated Debye temperature values were in good agreement with experimental and other theoretical results. A half metallic to metallic transition was also observed in REH3 under high pressure. Ferromagnetism was quenched in these hydrides at high pressures.

Probing martensitic transformation,kinetics,elastic and magnetic properties of Ni2-xMn1.5In0.5Cox alloys

The martensitic transformation,kinetics,elastic and magnetic properties of the Ni2-xMn1.5In0.5Cox(x=0-0.33)ferromagnetic shape memory alloys were investigated experimentally and theoretically by first-principles calculations.First-principles calculations show that Co directly occupies the site of Ni sublattice,and Co atoms prefer to distribute evenly in the structure.The optimized lattice constants are consistent with the experimental results.The martensitic transformation paths are as follows:PA↔FA↔6MFIM↔NMFIM when 0≤x<0.25;PA↔FA↔6MFM↔NMFIM with 0.25≤x<0.3 and PA↔FA↔NMFM with 0.3≤x≤0.33 for Ni2-xMn1.5In0.5Cox(x=0-0.33)alloys.The fundamental reasons for the decrease of TM with increasing Co content are explained from the aspects of first-principles calculations and martensitic transformation kinetics.The component interval of the magnetostructural coupling is determined as 0≤x≤0.25 by first-principles calculations.Furthermore,the origin of the demagnetization effect during martensitic transformation is attributed to the shortening of the nearest neighboring distances for Ni-Ni(Co)and Mn-Mn.Combining the theoretical calculations with experimental results,it is verified that the TM of the Co6 alloy is near room temperature and its magnetization differenceM is 94.6 emu/g.Therefore,magnetic materials with high performance can be obtained,which may be useful for new magnetic applications.