Electronic properties and surface states of RbNi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg" display="inline" id="d1e205"><mml:msub><mml:mrow /><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>Se<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg" display="inline" id="d1e213"><mml:msub><mml:mrow /><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>

Iron-based superconductors, with the ThCr2Si2-type tetragonal structure (122 family), due to iron arsenide/selenide layers exhibit several characteristic electronic properties. For example, multiband character mostly associated d-orbitals of and quasi-two-dimensional (2D) cylindrical Fermi surface. Moreover, external hydrostatic pressure leads isostructural phase transition from collapsed-tetragonal phase. In this paper, in relation iron-based we discuss properties novel 122-family member RbNi2Se2 (Liu et al., 2022). We show that two pockets quasi-2D character. Calculation surface spectral function for (001) shows states are realized independently on termination. Additionally, contrary 122 compounds, exhibits extraordinary multiple transitions under pressure. Lifshitz occurs pressure, which results into a strong modification shapes pockets.