  The discovery of MAX phase borides has added a new dimension for research in
the materials science community. In this paper, a first-principles study of the
newly known MAX phase borides Zr2AB2 (A = In, Tl) has been carried out. The
estimated lattice constants and volumes of the unit cell are found to be
consistent with previous study. The dynamical and mechanical stability of the
titled compounds have been checked. Fundamental insights into the stiffness
constants, elastic moduli, hardness parameters, brittleness and anisotropy
indices are presented. The Variation of these mechanical properties was
explained based on the Mulliken population analysis and charge density mapping
(CDM). The electronic properties have been dealt with by considering electronic
band structure and density of states (DOS) which confirmed the metallic nature
of Zr2AB2 (A = In, Tl). The lowly dispersive energy bands along the c-direction
confirmed anisotropy in conductivity. The analysis of DOS revealed the dominant
contribution from Zr-d orbitals to the conductivity with a small contribution
from the In/Tl-p states contributing at the Fermi level. The Debye temperature
(Theta-D), minimum thermal conductivity (Kmin), Gruneisen parameter and melting
temperature (Tm) have been calculated. The higher values of Theta-D and Tm, and
lower value of Kmin for Zr2AB2 (A = In, Tl) compared to those of Zr2AC (A = In,
Tl). Besides, the specific heat capacities, thermal expansion coefficient, and
different thermodynamic potential functions have been calculated. The optical
constants have been studied to reveal their possible relevance for application
purposes. The reflectivity spectra revealed the applicability of Zr2AB2 (A =
In, Tl) as cover materials to diminish the solar heating. The studied physical
properties of Zr2AB2 (A = In, Tl) are compared with those of other relevant 212
and 211 MAX phase nanolaminates.
