Atomic Diffusion in α-iron across the Curie Point: An Efficient and Transferable Ab Initio-Based Modeling Approach.

An accurate prediction of atomic diffusion in Fe alloys is challenging due to thermal magnetic excitations and magnetic transitions. We propose an efficient approach to address these properties via a Monte Carlo simulation, using ab initio-based effective interaction models. The temperature evolution of self- and Cu diffusion coefficients in α-iron are successfully predicted, particularly the diffusion acceleration around the Curie point, which requires a quantum treatment of spins. We point out a dominance of magnetic disorder over chemical effects on diffusion in the very dilute systems.

Equilibrium Vacancy Concentration Driven by Undetectable Impurities.

By means of ab initio calculations combined to statistical mechanics, we provide new evidence that an experimentally undetectable tiny amount of impurities can be responsible for drastic changes in vacancy concentrations ([V]), inducing large deviations from an Arrhenius law even at low temperature. It is the case of O and N in α-Fe. The present finding is fully compatible with existing experiments, and changes the previous common vision that C has the dominant effect. This study provides a route for bridging the longstanding theoretical-experimental gap on the prediction of [V] in metals.

Moderation effects of perfectionism and discrimination on interpersonal factors and suicide ideation.

This study examined the moderating effects of 3 risk factors-perfectionistic personal discrepancy, perfectionistic family discrepancy, and discrimination-on the associations between interpersonal risk factors (i.e., perceived burdensomeness and thwarted belongingness) and suicide ideation in a sample of 466 Asian international students studying in the United States. We focused specifically on perceived discrimination and maladaptive perfectionism as moderating risk factors to Joiner's (2005) interpersonal theory of suicidal behavior. We incorporated both personal and family discrepancy as indicators of maladaptive perfectionism. Personal discrepancy refers to the tendency of individuals to perceive that they failed to meet their own standards, whereas family discrepancy refers to individuals' tendency to perceive that they failed to meet their families' standards. Results highlight the significance of studying this overlooked population in the suicide ideation literature. Maladaptive perfectionism (i.e., personal and family discrepancy) as well as discrimination were found to be positively associated with suicide ideation. Moreover, family discrepancy and perceived discrimination were found to intensify the associations between interpersonal risk factors (i.e., perceived burdensomeness and thwarted belongingness) and suicide ideation. These findings underscore the importance of considering interpersonal factors in addressing suicidal risks with populations from collectivistic cultures. Research and clinical implications are also addressed.

Perfectionism in gifted students: moderating effects of goal orientation and contingent self-worth.

We examined the moderating effects of mastery goals and academic contingency of self-worth (CSW-A) on how perfectionistic discrepancy associates with academic efficacy and satisfaction with life among gifted students in middle and high school. Participants in this study were 144 gifted students from 6th to 12th grade in a suburban Midwest U.S. school district. A significant three-way interaction effect was found among discrepancy, mastery goals, and CSW-A on academic self-efficacy. The findings suggest that having high mastery goals served as a protective factor against the negative impact of discrepancy on academic efficacy for gifted students, but only for those with low CSW-A. For gifted students with elevated CSW-A, discrepancy was not negatively associated with academic self-efficacy, regardless of their level of mastery goals. The implications for these findings are discussed.

Profiles of acculturative adjustment patterns among Chinese international students.

This is the first study to empirically identify distinct acculturative adjustment patterns of new international students over their first 3 semesters in the United States. The sample consisted of 507 Chinese international students studying in the United States. Using psychological distress as an indicator of acculturative adjustment, measured over 4 time points (prearrival, first semester, second semester, and third semester), 4 distinct groups of student adjustment trajectories emerged: (a) a group exhibiting high levels of psychological distress across each time point (consistently distressed; 10%), (b) a group with decreasing psychological distress scores from Time 1 to Time 2 (relieved; 14%), (c), those with a sharp peak in psychological distress at Time 2 and Time 3 (culture-shocked; 11%), and (d) a group with relatively consistent low psychological distress scores (well-adjusted; 65%). Moreover, significant predictors of a better acculturative adjustment pattern included having higher self-esteem, positive problem-solving appraisal, and lower maladaptive perfectionism prior to the acculturation process. In addition, during the first semester of studying in the United States, having a balanced array of social support and using acceptance, reframing, and striving as coping strategies were associated with a better cross-cultural transition. Practical implications and future directions were also discussed.

Structure and magnetism of bulk Fe and Cr: from plane waves to LCAO methods.

Magnetic, structural and energetic properties of bulk Fe and Cr were studied using first-principles calculations within density functional theory (DFT). We aimed to identify the dependence of these properties on key approximations of DFT, namely the exchange-correlation functional, the pseudopotential and the basis set. We found a smaller effect of pseudopotentials (PPs) on Fe than on Cr. For instance, the local magnetism of Cr was shown to be particularly sensitive to the potentials representing the core electrons, i.e. projector augmented wave and Vanderbilt ultrasoft PPs predict similar results, whereas standard norm-conserving PPs tend to overestimate the local magnetic moments of Cr in bcc Cr and in dilute bcc FeCr alloys. This drawback is suggested to be closely correlated to the overestimation of Cr solution energy in the latter system. On the other hand, we point out that DFT methods with very reduced localized basis sets (LCAO: linear combination of atomic orbitals) give satisfactory results compared with more robust plane-wave approaches. A minimal-basis representation of '3d' electrons comes to be sufficient to describe non-trivial magnetic phases including spin spirals in both fcc Fe and bcc Cr, as well as the experimental magnetic ground state of bcc Cr showing a spin density wave (SDW) state. In addition, a magnetic 'spd' tight binding model within the Stoner formalism was proposed and validated for Fe and Cr. The respective Stoner parameters were obtained by fitting to DFT data. This efficient semiempirical approach was shown to be accurate enough for studying various collinear and non-collinear phases of bulk Fe and Cr. It also enabled a detailed investigation of different polarization states of SDW in bcc Cr, where the longitudinal state was suggested to be the ground state, consistent with existing experimental data.

Stability and mobility of mono- and di-interstitials in alpha-Fe.

We report a detailed ab initio study of the stability and migration of self-interstitial atoms (SIAs) and di-interstitials (di-SIAs) in alpha-Fe. The <110> dumbbell is confirmed to be the most stable SIA configuration, 0.7 eV below the <111> dumbbell. The lowest-energy migration path corresponds to a nearest-neighbor translation-rotation jump with a barrier of 0.34 eV. The most stable configuration for di-SIAs consists of <110> parallel dumbbells. Their migration mechanism is similar to that for SIAs, with an activation energy of 0.42 eV. These results are at variance with predictions from existing empirical potentials and allow one to reconcile theory with experiments.