Phononic properties of cinnabar: Ab initio calculations and new experimental results R.K. Kremer, M. Cardona, R. Lauck, G. Siegle, A. Mu˜ noz 1 , A.H. Romero 2 and M. Schmidt 3 Cinnabar (α-HgS) is the main ore for the pro- duction of mercury and, in powdered form, con- stitutes the red pigment vermillion which was already used in pre-Columbian Peru as early as 500 BC (Chavin Empire). Large scale min- ing of cinnabar is known to have taken place after the conquest of the Inca Empire (1532 AD) in connection with the extraction of silver from low grade ores. It probably led to the first pre-industrial source of Hg environmental pol- lution. Evidence for the use of cinnabar as a pig- ment is also found in Mesoamerica, dating back to the Olmec culture (≈ 800 BC), where it was utilized in ceremonial burials and for coloring beautiful ceramic figurines. In the Eastern World, China, today the main producer of mercury, was early using cinnabar as a pigment. The best known use is found in the lacquerware of the Song Dynasty (1000 AD). Cinnabar is applied, still today, in traditional Chinese medicine (as Zhu Sha) to treat a variety of ailments including colds, insomnia, restless- ness and, less dangerously since applied exter- nally, skin disorders. Because of the existence of large cinnabar deposits, vermillion was also used in Spain and Italy to illuminate ancient manuscripts. The extraction of mercury from cinnabar is al- ready documented in Teophrastus of Eresus’ ‘Book on Stones’ (≈ 315 BC): ‘Native cinnabar was rubbed with vinegar in a copper mortar with a copper pestle’, thus describing what is probably the first mechano-chemical reac- tion. Pliny the Elder (23-79 AD), in his natu- ral history [1], describes not only the mechano- chemical but also the distillation method which seems to have originated from Dioscorides (40–90 AD). Cinnabar is the stable form of HgS under nor- mal temperature and pressure. Besides, a zinc- blende-type modification of HgS, metacinnabar (β-HgS), also exists. We have described its elec- tronic and vibronic properties in the Annual Re- port of 2009. Despite the wide technological importance of cinnabar there is limited knowledge of its elec- tronic and lattice dynamical properties. In this contribution we focus on the phonon and ther- modynamic properties of cinnabar. Especially, we calculate the phonon dispersion relations and compare theoretical results with our new experimental data and data available in the lit- erature. The reader may find a more detailed discussion of the electronic structure and de- rived optical properties of cinnabar including a comparison of the calculated dielectric function with unpublished experimental data in [2]. Cinnabar has two chiral (enantiomorphic) struc- ture modifications (space groups no. 152 (D 4 3 ) and no. 154 (D 6 3 ), the primitive cell is composed of two coaxial helices, one with three S atoms, the other with three Hg atoms). These modifi- cations rotate the plane of polarization of light propagating along the c-axis in opposite direc- tions (optical activity). The ab initio calculations have been performed with two different implementations of Density Functional Theory, the VASP and the ABINIT code [2]. The latter was used to obtain the vibra- tional properties. To this end the dynamical ma- trices were calculated for a grid of 6×6×3 and four different grid shifts, with a total of 83 ma- trices (including the Γ point) and a Fourier in- terpolation was carried out in order to increase the density of q points. We display in Fig. 1 the phonon dispersion re- lations of cinnabar. The 6 atoms per primi- tive cell give rise to 18 vibrational modes, 3 of which have zero frequency at Γ (acoustic modes). Thus we are left with 15 modes, 5 Γ 3 doublets (ir and Raman active), 2 Γ 1 singlets (Raman active) and 3 Γ 2 singlets (ir active). The 1