Microscopic Modelling of Correlated Low-dimensional Systems

List of Figures x
5.1 Comparison between the total and partial DOS obtained for (a) the polymer
without relaxation (experimental structure) CuCCP and (b) the relaxed
CuCCP polymer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
5.2 Orbital resolved DOS for the relaxed structure CuCCP. The contribution of
the Cu s/O s/N1 s states are smaller than 0.1 % in this region and therefore
are not shown. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.3 Band structure for the relaxed Cu(II) polymer CuCCP in the GGA approximation
along the path [22] F(0, 1, 0)-Γ(0, 0, 0)-Z(0, 0, 1)-B(0.99, −0.13, 0)-
Γ(0, 0, 0) in units of π/a, π/b, π/c. The bars indicate the dominant band
character in the local coordinate frame of Cu (see text for explanation). . . 78
5.4 Cu-Cu interaction paths ti, where the index i = 1, 2, 3, 7, 8 denotes the ith
neighbor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.5 Partial spin-polarized DOS for the relaxed CuCCP compound. In it the
contribution from spin up (upper panel) and spin down (lower panel) are
shown. For simplicity the total density of states have been removed. . . . . 81
5.6 Band structure for CuCCP in the spin-polarized calculation. (a) spin up and
(b) spin down. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
5.7 Four unit cells of CuCCP where two hydrogen atoms in the hydroquinone
rings have been substituted by two amino groups. Notice the tilting of the
hydrogen atoms belonging to the molecule NH2. . . . . . . . . . . . . . . . . 83
5.8 Orbital resolved DOS for (a) Cu(II)-NH2 and (b) Cu(II)-CN; (c) comparison
between the contribution of NH2 and CN groups to the DOS at EF in a
blown up scale, the green line indicates the contribution of the N s states in
this energy range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5.9 Comparison of the band around the Fermi level between (from top to bottom)
the relaxed CuCCP, Cu(II)-NH2 and Cu(II)-CN respectively. In all cases the
same path in the irreducible FBZ described for CuCCP was used. . . . . . . 86
5.10 3D charge density in the energy isovalue ρ = 0.003 e/˚A 3 for (a) relaxed
CuCCP polymer, (b) Cu(II)-NH2 polymer, and (c) Cu(II)-CN polymer; (d)
indicates the atom positions common to (a)-(c). The N-C-C-C-H chain of
atoms appearing above the chains belongs to the next layer. . . . . . . . . . 88
5.11 Crystal structure of the Cu(II) polymer with water ligands (Cu(II)-H2O).
Shown are also the unit cell (vectors a, b and c) and the hydrogen bonds
(dashed lines). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
5.12 Crystal structure of the Cu(II) polymer with ammonia ligands (Cu(II)-NH3).
Shown are also the unit cell (vectors a, b and c) and the hydrogen bonds
(dashed lines). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.13 Orbital resolved DOS for (a) Cu(II)-H2O and (b) Cu(II)-NH3. . . . . . . . 92
5.14 Band structure of Cu(II)-H2O compound. (a) the bars indicate the dominant
band character in the local coordinate frame of Cu (see text for explanation)
(b) detailed plot of the band structure around the Fermi level. . . . . . . . 93
5.15 Band structure of Cu(II)-NH3 compound. (a) the bars indicate the dominant
band character in the local coordinate frame of Cu (see text for explanation.)
(b) detailed plot of the band structure around the Fermi level. . . . . . . . 95