Fundamental Gaps in Cr_{8}, Cr_{7}Ni and Cr_{7}Cd Molecules

Abstract

In this paper we investigate fundamental gaps of three octametallic Cr-based molecular rings Cr8F8(Piv)16, Cr7NiF8(Piv)16 and Cr7CdF8(Piv)16 using the SIESTA package. We nd that for the ground-state antiferromagnetic congurations, the gap of the homometallic ring is signicantly higher than those of the heterometallic rings. In addition, the HOMO and LUMO orbitals are plotted and discussed.

The Study of Magnetic Molecules Containing Cr9 Chromium-Based Rings within Density Functional Theory

“…Interesting behavior is observed for the third molecule C where HOMO levels are located on disconnected pivalic group, while LUMO levels are mainly delocalized over a large portion of the ring. These results are similar to the ones obtained for heteronuclear octametallic Cr 7 Cd and Cr 7 Ni rings in [8]. In the heterometallic rings the HOMO levels were strongly localized on a substituting ions Cd and Ni which can be considered analogous to the unique Cr pair in Cr 9 rings.…”

“…By performing two calculations [7,8] of the KohnSham high occupied molecular orbital (HOMO) energy, one for the N particle system and another for the N + 1 particle system with 1 extra electron one can obtain estimates of the fundamental gap as Table II.…”

“…Following the established methodology [6,9] and comparing combinations of DFT energy differences with those of the Ising models, we have estimated the exchange integrals J between chromium ions within the standard broken symmetry approach [9] for three different models of couplings α, β and γ. In the first model α we consider J for nearest neighbours (NN) for eight pairs of Cr ions for the chromium ion pairs (1,2) and (8,9). The exchange interaction parameters obtained for Cr 9 are presented in Table III.…”

DFT Estimation of Exchange Coupling Constant of Cr8Molecular Ring using the Hybrid Functional B3LYP

“…We will particularly address the persisting problem of coupling constant signicantly overestimated in previous calculations for Cr 8 ring [3,4,914] as well as for other chromium based molecules [5,9,15,16].…”

“…The exact chemical formula of the ring is Cr 8 F 8 (Piv) 16 . The Piv group is pivalic acid trimethyl acetic acid CO 2 − C(CH 3 ) 3 .…”