Angle resolved as well as angle integrated photoemission in the soft and hard X-ray regime became a very important tool to investigate the bulk properties of various materials [1]. Contrary, bulk sensitivity can be achieved by so called threshold photoemisison, e.g. by using for example  laser light at 405 nm [2]. The increased bulk sensitivity might lead to the impression that the LSDA band structure or density of states can be directly compared to the measured spectra. However, various important effects, like matrix elements, the photon momentum or phonon excitations, are in this way neglected. Here, we present a generalization of the state of the art description of the photoemisison process, the so called one-step model that describes excitation, transport to the surface and escape into the vacuum in a coherent way.  A short introduction to the main features of the one-step model implementation within the Munich SPR-KKR program package will be given. Special emphasis will be put on the spin-polarised relativistic mode that allows to deal with magnetic dichroism. Also, the possibility to account for correlation effects and chemical disorder using the LSDA+DMFT (dynamical mean field theory) scheme in combination with the Coherent Potential Approximation (CPA) method [3] will be demonstrated by various examples. For photon energies, even in the soft-x-ray regime, a considerable effect of  lattice vibrations is present [4]. Here, we discuss a theoretical description of lattice vibrations which is based on the CPA. These aspects will be discussed in an detail using various examples [5]. In the last part of my talk I will show prediction that HAXPES is possibly valuable tool to study topological surface states and rashba effect [6].

1. Probing bulk electronic structure with hard X-ray angle-resolved photoemission
   A. X. Gray, C. Papp, S. Ueda, B. Balke, Y. Yamashita, L. Plucinski, J. Minár, J. Braun, E. R. Ylvisaker, C. M. Schneider, W. E. Pickett, H. Ebert, K. Kobayashi & C. S. Fadley, Nat. Materials 10, 759 (2011).
2. M. Kronseder, Ch. Back, J. Minar et al.,
   Phys. Rev. B 83, 132404 (2011)
3. J. Minar, J. Phys.: Cond. Mat. Topical review 23, 253201 (2011),
   H. Ebert et al., Rev. Prog. Phys. 74, 096501 (2011)
4. J. Braun, J. Minar et al., Phys. Rev. B 88, 205409 (2013)
5. Bulk electronic structure of the dilute magnetic semiconductor Ga_1−xMn_xAs through hard X-ray angle-resolved photoemission
   A. X. Gray, J. Minár, S. Ueda, P. R. Stone, Y. Yamashita, J. Fujii, J. Braun, L. Plucinski, C. M. Schneider, G. Panaccione, H. Ebert, O. D. Dubon, K. Kobayashi & C. S. Fadley, Nature materials 11, 957 (2012),
   Fujii et al., Phys. Rev. Lett.  111, 097201 (2013)
6. Exceptional behavior of d-like surface resonances on W(110): the one-step model in its density matrix formulation
   J. Braun, K. Miyamoto, A. Kimura, T. Okuda, M. Donath, H. Ebert and J. Minár; New J. Phys 16, 015005 (2014)