Since each Bravais lattice
unit cell of the graphene sheet includes [N.sub.a] = 2 atoms, the Hamiltonian of the trilayers graphene, [N.sub.p] = 3, as a typical case, would be introduced by a 6 x 6 matrix with the following basis kets of the Hilbert space,
As a theoretical physicist, Ashcroft could not really establish if metallic hydrogen at absolute zero 1) acted as a two component Fermi liquid, 2) behaved much like the unusual theoretical one-component plasma [54, 55], or 3) retained the essential characteristic of a Bravais lattice, an ordered proton field with fully degenerate electrons.
The work supported Wigner and Huntington's  contention that a layered Bravais lattice form of metallic hydrogen was the most stable in the 380[+ or -]50 to 860[+ or -] 100 GPa range .
Table 4 shows that most organic compounds crystallize in a triclinic, monoclinic, or orthorhombic Bravais lattice with the primitive lattice (87.1 %) by far the most common.
But as Table 9 illustrates, for the cubic F original cell, six of the sublattices (\X\ = 1/2) have identical reduced forms (i.e., reduced form 23 = C-centered Bravais Lattice).
They discuss the 14 Bravais lattices
and the reciprocal to them, basic concepts of point group symmetry, the crystal structure and lattice constants of most elements and about 650 binary compounds.
Two model examples--hexamethylbenzene, a centrosymmetric crystal with both covalent and Van der Waals bonds, and anhydrous alum, a nocentrosymmetric structure typical of ceramics and metals--are chosen as model crystals and used to explain symmetry, point groups, space groups, Bravais lattices
, reciprocal lattices, and diffraction maxima.