Barium sulfide (BaS) is an important precursor to other barium compounds with applications from ceramics and flame retardants to luminous paints and additives, and recent research shows potential technological applications in electrical and optical devices. Under normal conditions, BaS crystallizes in the NaCl type of structure, and with the increase in pressure BaS undergoes a structural phase transition to a CsCl type modification. This study presents modeling of barium sulfide under pressure with special focus on structural aspects and electronic properties. We predict metastable BaS polymorphs which have not yet been observed in the experiment or in previous calculations, and we investigated their vibrational and thermodynamical properties. Furthermore, we investigate the electronic properties of experimentally known structures as well as novel predicted modifications of BaS on ab initio level using Hartree-Fock, GGA-PBE, and the hybrid B3LYP functional. In this way, we address new possibilities of synthesizing BaS and possible band gap tuning which can have great applications in optoelectrical technologies.

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New crystalline modifications of the technologically important compound CoMoO 4 would be of great importance. Thus, the simple and fast Self-Propagating Room Temperature procedure (SPRT) was used to synthesize crystalline phases of CoMoO 4 at room temperature. X-ray powder diffraction (XRPD) revealed that the synthesized material consists of two phases: CoMoO 4 (I) and CoMoO 4 (II), both with the monoclinic space group C2/m, No.12. This experimental exploration of the phase space of CoMoO 4 was complemented by theoretical efforts. These consisted of a global search for structure candidates in the CoMoO 4 system using fast empirical potentials. Eleven additional structure candidates have been found, several of which might be accessible to synthesis and/or shed light on other cobalt-molybdenum oxides whose structure and composition are under discussion.

Abstract. Transition metal silicides have attracted great attention due to their potential applications in microelectronics, ceramics, and the aerospace industry. In this study, experimental and theoretical investigations of tungsten based silicides were performed. Tungsten disilicide (WSi 2 ) was synthesized by simple thermal treatment at 1350°C for 4 h in an argon atmosphere. These optimal synthesis conditions were obtained by variation of temperatures and times of heating, and the

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