Konrad, Jerzy Kapcia2021-11-042021-11-042021-09-03Journal of Magnetism and Magnetic Materials 541, 168441 (2022)0304-8853https://hdl.handle.net/10593/26462This is the author created version of an article accepted for publication in J. Magn. Magn. Matter (Elsevier) journal. The article has been published on a gold open access basis under a CC BY 4.0 licenceThe extended Hubbard model in the atomic limit, which is equivalent to lattice S=1/2 fermionic gas, is considered on the triangular lattice. The model includes onsite Hubbard U interaction and both nearest-neighbor (W1) and next-nearest-neighbor (W2) density-density intersite interactions. The variational approach treating the $U$ term exactly and the $W_l$ terms in the mean-field approximation is used to investigate thermodynamics of the model and to find its finite temperature (T>0) phase diagrams (as a function of particle concentration) for W1>0 and W2<0. Two different types of charge-order (i.e., DCO and TCO phases) within $\sqrt{3} \times \sqrt{3}$ unit cells as well as the nonordered (NO) phase occur on the diagram. Moreover, several kinds of phase-separated (PS) states (NO/DCO, DCO/DCO, DCO/TCO, and TCO/TCO) are found to be stable for fixed concentration. Attractive W2}<0 stabilizes PS states at T=0 and it extends the regions of their occurrence at T>0. The evolution of the diagrams with increasing of |W2|/W1 is investigated. It is found that some of the PS states are stable only at T>0. Two different critical values of |W2|/W1 are determined for the PS states, in which two ordered phases of the same type (i.e., two domains of the DCO or TCO phase) coexist.enginfo:eu-repo/semantics/openAccesscharge ordertriangular latticefermionic lattice gaslonger-range interactionsextended Hubbard modelatomic limitArtykułhttps://doi.org/10.1016/j.jmmm.2021.168441