ORALS

SESSION: SolidStateChemistryTuePM1-R6	Alario-Franco international Symposium (2nd Intl Symp on Solid State Chemistry for Applications & Sustainable Development)
Tue. 29 Nov. 2022 / Room: Andaman 1
Session Chairs: Hiroshi Kageyama; Session Monitor: TBA

14:50: [SolidStateChemistryTuePM107] OS
Fixing the Misuse of Cohesive-Energies in Modeling Transition Metals & Nanoalloys
Micha Polak¹ ; Leonid Rubinovich¹ ; ¹Ben-Gurion University of the Negev, Beer-Sheva, Israel;
Paper Id: 245 [Abstract]

In spite of free-atom electronic-relaxation contributions to transition-metal cohesive-energies (E_coh), numerous studies have misused the latter instead of using genuine interatomic bond-energies (E_b) in modeling bulk and surface properties [1-2], including atomistic-potential parametrization for nanoalloys. The required E_coh modification consists of s to d electronic promotion energy plus the magnetic spin-polarization energy (in accordance with Hund’s first rule). The latter was computed [3] for the 3d, 4d and 5d series using the local spin-density approximation (LSDA), whereas the former was obtained from spectroscopic data. This work first reveals that eliminating these free-atom contributions from experimental cohesive-energies leads to highly accurate linear correlations of the resultant bond-energies with melting temperatures and enthalpies, as well as with inverse thermal-expansion coefficients, specifically for the fcc transition-metals. In addition, predictions of surface segregation phenomena in Cu-Pd and Au-Pd bulk alloys on the basis of the correct energetics are in much better agreement with reported LEISS experimental results. A distinctive demonstration of the problem and its solution involves the significant impact of the cohesive-energy modification on segregation (separation) phase transitions in Cu-Ni truncated-octahedron nanoalloys. In particular, without the correction destabilization of Janus configuration in favor of core-shell is erroneously obtained. Preliminary computations for Cu-Ni-Pd ternary nanoalloys reveal significant effects of Pd and of the fixed energetics on chemical-order and transition temperatures. Generally, the introduced correction procedure should be applicable also to other bond-energy related properties of any transition metals, alloys as well as nanoalloys.

References:
REFERENCES:
[1] R. Vardi, L. Rubinovich, M. Polak, Surf. Sci. 602 (2008) 1040-1044.
[2] M. Polak and L. Rubinovich, J. Phys.: Condens. Matter 31 (2019) 215402.
[3] M.S.S. Brooks and B. Johansson, J. Phys. F: Met. Phys. 13 (1983) L197-L202.