Under suitable circumstances imperfections in semiconductors can bind electrons (holes) with a binding energy small compared to the intrinsic energy gap of the host; the wavefunctions characterising the energy levels of the imperfection are extended over many lattice spacings. This review discusses the electronic energy levels of chemical impurities in the classic group IV elemental and the 111-V and 11-VI compound semiconductors. The large dielectric constant of the host, the anisotropic effective mass tensor and/or the small effective mass of the charge carrier are the factors which play a significant role in the description of the electronic energy levels; they can be viewed as scaled-down versions of the hydrogen atom with bound states having binding energies orders of magnitude smaller than those of the hydrogen atom. In this review we present the experimental results on the spectroscopy of donors and acceptors in semiconductors together with the theory necessary for their interpretation. We discuss the experimental results and the theory of the bound states of impurities in the context of the symmetry and the effective-mass parameters of the band extrema with which they are associated. Effects of external perturbation-piezo-and magneto-spectroscopy-are presented both from experimental and theoretical points of view. The review concludes with the experimental observations on the linewidths of the excitation spectra of donors and acceptors in semiconductors and an analysis of the causes underlying them.

Using the modified formalism of [Dorogokupets, Oganov, 2005, 2007, equations of state are developed for diamond, Ag, Al, Au, Cu, Mo, Nb, Pt, Ta, and W by simultaneous optimization of shock-wave data, ultrasonic, X-ray, dilatometric and thermochemical measurements in the temperature range from ~100 K to the melting temperature and pressures up to several Mbar, depending on the substance. The room-temperature isotherm is given in two forms: (1) the equation from [Holzapfel, 2001[Holzapfel, , 2010 which is the interpolation between the low pressure (x≥1) and the pressure at infinite compression (x=0); it corresponds to the Thomas-Fermi model, and (2) the equation from [Vinet et al., 1987]. The volume dependence of the Grüneisen parameter is calculated according to equations from [Zharkov, Kalinin, 1971;Burakovsky, Preston, 2004] with adjustable parameters, t and δ. The room-temperature isotherm and the pressure on the Hugoniot adiabat are determined by three parameters, K', t and δ, and K 0 is calculated from ultrasonic measurements. In our study, reasonably accurate descriptions of all of the basic thermodynamic functions of metals are derived from a simple equation of state with a minimal set of adjustable parameters.The pressure calculated from room-temperature isotherms can be correlated with a shift of the ruby R1 line. Simultaneous measurements of the shift and unit cell parameters of metals are conducted in mediums containing helium [Dewaele et al., 2004b;2008;Takemura, Dewaele, 2008;Takemura, Singh, 2006], hydrogen [Chijioke et al., 2005] and argon [Tang et al., 2010]. According to [Takemura, 2001], the helium medium in diamond anvil cells provides for quasi-hydrostatic conditions; therefore, the ruby pressure scale, that is calibrated for the ten substances, can be considered close to equilibrium or almost absolute. The ruby pressure scale is given as P(GPa)=1870⋅Δλ/λ 0 ⋅(1+6⋅Δλ/λ 0 ). The room-temperature isotherms corrected with regard to the ruby scale can also be considered close to equilibrium or almost absolute. Therefore, the equations of state of the nine metals and diamond, which are developed in our study, can be viewed as almost absolute equations of state for the quasi-hydrostatic conditions. In other words, these equations agree with each other, with the ruby pressure scale, and they are close to equilibrium in terms of thermodynamics. The PVT relations derived from these equations can be used as mutually agreed pressure scales for diamond anvil cells in studies of PVT properties of minerals in a wide range of temperatures and pressures. The error of the recommended equations of the state of substances and the ruby pressure scale is about 2 or 3 per cent. Calculated PVT relations and thermodynamics data are available at http://labpet.crust.irk.ru.

The effects of zero-point motion and the anharmonicity of the lattice vibrations of diamond have been explored theoretically in the context of a valence force model explicitly incorporating the isotopic composition. The predictions are tested in a study of the elastic moduli (c i j ) deduced from Brillouin spectra and the zone center optical mode frequency ( 0 ) from Raman spectra of isotopically controlled diamond specimens. On the basis of the anharmonicity parameter of the model associated with bond stretching, deduced from a comparison of the theory with experimentally reported dependence of the lattice parameter with the atomic fraction of 13 C in 12 C 1Ϫx 13 C x diamond, it is predicted that the bulk modulus of 13 C diamond exceeds that for 12 C diamond by one part in a thousand, just below the experimental sensitivity accessible with Brillouin measurements; 0 exceeds the value expected from the M Ϫ1/2 dependence, where M is the average atomic mass, by ϳ 0.3 cm Ϫ1 , consistent with observation. The Grüneisen parameter for 0 and the third-order bulk modulus are consistent with the theoretical estimates from the present model. The elastic moduli for natural diamond determined in the present study, viz., c 11 ϭ10.804(5), c 12 ϭ1.270(10), and c 44 ϭ5.766(5) in units of 10 12 ͑dyn/cm 2 ) are the most accurate yet obtained. ͓S0163-1829͑96͒03330-9͔

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