000 03786nam a22004575i 4500
001 978-3-642-23238-1
003 DE-He213
005 20140220083301.0
007 cr nn 008mamaa
008 110922s2012 gw | s |||| 0|eng d
020 _a9783642232381
_9978-3-642-23238-1
024 7 _a10.1007/978-3-642-23238-1
_2doi
050 4 _aQC611.9-611.98
072 7 _aTJFD5
_2bicssc
072 7 _aTEC039000
_2bisacsh
072 7 _aSCI021000
_2bisacsh
082 0 4 _a530.41
_223
100 1 _aO'Regan, David D.
_eauthor.
245 1 0 _aOptimised Projections for the Ab Initio Simulation of Large and Strongly Correlated Systems
_h[electronic resource] /
_cby David D. O'Regan.
264 1 _aBerlin, Heidelberg :
_bSpringer Berlin Heidelberg,
_c2012.
300 _aXVI, 216 p.
_bonline resource.
336 _atext
_btxt
_2rdacontent
337 _acomputer
_bc
_2rdamedia
338 _aonline resource
_bcr
_2rdacarrier
347 _atext file
_bPDF
_2rda
490 1 _aSpringer Theses
505 0 _aAn Introduction to Linear-Scaling Ab Initio Calculations -- Linear-Scaling DFT+U for Large Strongly-Correlated Systems.-  Projector Self-Consistent DFT+U Using Nonorthogonal Generalised Wannier Functions.-Linear-Scaling Ab Initio Calculations.-Linear-Scaling DFT+U for Large Strongly Correlated Systems.-  Optimised Projections for Strongly-Correlated Subspaces -- Projector Self-Consistent DFT +U Using Nonorthogonal  Generalised Wannier Functions -- Subspace Representations in Ab Initio Methods for Strongly Correlated Systems -- Tensorial  Consequences of Projection Optimisation -- Geometric Aspects of Representation Optimisation.-  A Numerical Study of Geometric Corrections for Representation Optimisation -- Tensorial Aspects of Calculating Hubbard U Interaction Parameters -- Discussion and Conclusion -- Appendix: Geometric Observations.
520 _aDensity functional theory (DFT) has become the standard workhorse for quantum mechanical simulations as it offers a good compromise between accuracy and computational cost. However, there are many important systems for which DFT performs very poorly, most notably strongly-correlated materials, resulting in a significant recent growth in interest in 'beyond DFT'  methods. The widely used  DFT+U technique, in particular, involves the addition of explicit Coulomb repulsion terms to reproduce the physics of spatially-localised electronic subspaces. The magnitude of these corrective terms, measured by the famous Hubbard U parameter, has received much attention but less so for the projections used to delineate these subspaces. The dependence on the choice of these projections is studied in detail here and a method to overcome this ambiguity in DFT+U, by self-consistently determining the projections, is introduced. The author shows how nonorthogonal representations for electronic states may be used to construct these projections and, furthermore, how DFT+U may be implemented with a linearly increasing cost with respect to system size. The use of nonorthogonal functions in the context of electronic structure calculations is extensively discussed and clarified, with new interpretations and results, and, on this topic, this work may serve as a reference for future workers in the field.
650 0 _aPhysics.
650 1 4 _aPhysics.
650 2 4 _aStrongly Correlated Systems, Superconductivity.
650 2 4 _aTheoretical, Mathematical and Computational Physics.
650 2 4 _aSolid State Physics.
710 2 _aSpringerLink (Online service)
773 0 _tSpringer eBooks
776 0 8 _iPrinted edition:
_z9783642232374
830 0 _aSpringer Theses
856 4 0 _uhttp://dx.doi.org/10.1007/978-3-642-23238-1
912 _aZDB-2-PHA
999 _c102143
_d102143