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The mechanical, thermal and dynamical stabilities, electronic structure, contact type, and height of the barrier at the interface of TaX 2 (X = S, Se, Te) and BY (Y = P, As, Sb) metal-semiconductor (MS) contact are investigated via first principles calculations. Binding energies, mechanical properties, phonon spectra and ab initio molecular dynamics (AIMD) simulations confirm the stabilities of these systems. TaX 2 -BY (X = S, Se, Te; Y = P, As, Sb) MS van der Waals heterostructures (vdWHs) are found to be metal with a Schottky contact at the interface. Formation of the n-type Schottky contact at the interface of TaX 2 -BY (X = S, Se, Te; Y = P, As, Sb) MS vdWHs favors electron conduction over hole conduction. Small (higher) effective mass (carrier mobility) make TaS 2 -BSb, TaSe 2 -BSb and TaTe 2 -BSb MS vdWHs, potential candidates for high speed nanoelectronic applications. Bader charge analysis shows that at the interface of TaX 2 -BY (X = S, Se, Te; Y = P, As, Sb) MS vdWHs, in TaX 2 (BP, BAs) the electrons transfer from the TaX 2 layer to the BP and BAs layer, while in TaX 2 (BSb) the electrons transfer from the BSb layer to TaX 2 layer., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In this paper, we use density functional theory (DFT) using full-potential linearized augmented plan wave plus local orbital method (FP-LAPW + lo). The structural, electronic, optical, photocatalytic, mechanical, vibrational, and thermodynamical behaviors of new double antiperovskite (DAP) Cs 6 AgBiX 2 (X = Cl, Br, I) were studied. The band structure was calculated with and without spin orbit coupling (SOC). Using the TB-mBJ approach (Hybrid) revealed bandgap values of 1.504 eV, 1.491 eV, and 1.392 eV for Cs 6 AgBiCl 2 , Cs 6 AgBiBr 2 , and Cs 6 AgBiI 2 , respectively. Optical characteristics were studied to ascertain the light absorbing ability of Cs 6 AgBiX 2 . The elastic and vibrational (phonon) properties demonstrate that Cs 6 AgBiCl 2 and Cs 6 AgBiBr 2 are stable but Cs 6 AgBiI 2 is not. The calculated optimal bandgap and high absorption coefficient of Cs 6 AgBiCl 2 and Cs 6 AgBiBr 2 , suggest their potential for solar cell applications. Moreover, our photocatalytic results suggest that these materials have high oxidizing capacity that can be used to efficiently produce oxygen cheaply using solar water splitting., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (This journal is © The Royal Society of Chemistry.)