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- N. Helbig
- 2015

Fractional snow-covered area (SCA) is a key parameter in large-scale hydrological, meteorological and regional climate models. Since SCA affects albedos and surface energy balance fluxes, it is especially of interest over mountainous terrain where generally a reduced SCA is observed in large grid cells. Temporal and spatial snow distributions are, however,… (More)

- S Sharma, J K Dewhurst, +6 authors E K U Gross
- Physical review letters
- 2007

A description of noncollinear magnetism in the framework of spin-density functional theory is presented for the exact exchange energy functional which depends explicitly on two-component spinor orbitals. The equations for the effective Kohn-Sham scalar potential and magnetic field are derived within the optimized effective potential (OEP) framework. With… (More)

- Iris Theophilou, Nektarios N Lathiotakis, Miguel A L Marques, Nicole Helbig
- The Journal of chemical physics
- 2015

Functionals of the one-body reduced density matrix (1-RDM) are routinely minimized under Coleman's ensemble N-representability conditions. Recently, the topic of pure-state N-representability conditions, also known as generalized Pauli constraints, received increased attention following the discovery of a systematic way to derive them for any number of… (More)

- Iris Theophilou, Nektarios N Lathiotakis, Nicole Helbig
- Journal of chemical theory and computation
- 2016

We consider necessary conditions for the one-body reduced density matrix (1RDM) to correspond to a triplet wave function of a two-electron system. The conditions concern the occupation numbers and are different for the high spin projections, Sz = ±1, and the Sz = 0 projection. Hence, they can be used to test if an approximate 1RDM functional yields the same… (More)

- N N Lathiotakis, N Helbig, A Zacarias, E K U Gross
- The Journal of chemical physics
- 2009

An approximation for the exchange-correlation energy of reduced-density-matrix-functional theory was recently derived from a study of the homogeneous electron gas [N. N. Lathiotakis, N. Helbig, and E. K. U. Gross, Phys. Rev. B 75, 195120 (2007)]. In the present work, we show how this approximation can be extended appropriately to finite systems, where the… (More)

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