Insights into Land Plant Evolution Garnered from the Marchantia polymorpha Genome.

The evolution of land flora transformed the terrestrial environment. Land plants evolved from an ancestral charophycean alga from which they inherited developmental, biochemical, and cell biological attributes. Additional biochemical and physiological adaptations to land, and a life cycle with an alternation between multicellular haploid and diploid generations that facilitated efficient dispersal of desiccation tolerant spores, evolved in the ancestral land plant. We analyzed the genome of the liverwort Marchantia polymorpha, a member of a basal land plant lineage. Relative to charophycean algae, land plant genomes are characterized by genes encoding novel biochemical pathways, new phytohormone signaling pathways (notably auxin), expanded repertoires of signaling pathways, and increased diversity in some transcription factor families. Compared with other sequenced land plants, M. polymorpha exhibits low genetic redundancy in most regulatory pathways, with this portion of its genome resembling that predicted for the ancestral land plant. PAPERCLIP

The Physics of the Hume-Rothery Electron Concentration Rule

For a long time we have shared the belief that the physics of the Hume-Rothery electron concentration rule can be deepened only through thorough investigation of the interference phenomenon of itinerant electrons with a particular set of lattice planes, regardless of whether d-states are involved near the Fermi level or not. For this purpose, we have developed the FLAPW-Fourier theory (Full potential Linearized Augmented Plane Wave), which is capable of determining the square of the Fermi diameter, ( 2 k F ) 2 , and the number of itinerant electrons per atom, e/a, as well as the set of lattice planes participating in the interference phenomenon. By determining these key parameters, we could test the interference condition and clarify how it contributes to the formation of a pseudogap at the Fermi level. Further significant progress has been made to allow us to equally handle transition metal (TM) elements and their compounds. A method of taking the center of gravity energy for energy distribution of electrons with a given electronic state has enabled us to eliminate the d-band anomaly and to determine effective ( 2 k F ) 2 , and e/a, even for systems involving the d-band or an energy gap across the Fermi level. The e/a values for 54 elements covering from Group 1 up to Group 16 in the Periodic Table, including 3d-, 4d- and 5d-elements, were determined in a self-consistent manner. The FLAPW-Fourier theory faces its limit only for elements in Group 17 like insulating solids Cl and their compounds, although the value of e/a can be determined without difficulty when Br becomes metallic under high pressures. The origin of a pseudogap at the Fermi level for a large number of compounds has been successfully interpreted in terms of the interference condition, regardless of the bond-types involved in the van Arkel-Ketelaar triangle map

Identification of the Brillouin zone planes in the Hume-Rothery matching rule and their role in the formation of pseudogap from ab initio band calculations for the Al-Mg-Zn 1/1-1/1-1/1 approximant

The Hume-Rothery matching rule has been widely used for many years as a practically useful guide to search for new quasicrystals and their approximants. In this work, we have performed the linear muffin-tin orbital atomic-sphere approximation band calculations for the nearly-free-electron-like Al_Mg_Zn_ 1/1-1/1-1/1 approximant. It is shown that highly degenerate free-electron states in the vicinity of the center of (543), (710), and (550) planes, whose reciprocal lattice vectors well coincide with the Fermi diameter 2k_F in the extended zone scheme, are all reduced to the regions centered at the point N corresponding to the center of the (110) zone planes in the reduced-zone scheme and that the lifting of these degenerate states leads to the sizable pseudogap at the Fermi level, thereby lowering the electronic energy in this system. This is, to our knowledge the first attempt to identify the Brillouin zone planes in the empirical Hume-Rothery rule and to extract their role in the formation of the pseudogap from ab initio band calculations

Interpretation of the Hume-Rothery electron concentration rule in the T2Zn11 (T=Ni, Pd, Co and Fe) γ-brasses based on first-principles FLAPW calculations

The first-principles full-potential augmented plane wave (FLAPW) band calculations were performed for a series of T_2Zn_ (T=Ni, Pd, Co, and Fe) γ brasses to elucidate the Hume-Rothery electron concentration rule. The pseudogap is found immediately below the Fermi level E_F in the Ni_2Zn_ and Pd_2Zn_ γ brasses. A resulting gain in the electronic energy is attributed to their stabilization in the same way as in Cu_5Zn_8 and Cu_9Al_4 previously studied. However, the pseudogap is essentially shifted above E_F in both Co_2Zn_ and Fe_2Zn_. The Fourier analysis of the FLAPW wave function was made at the symmetry point N of the reduced Brillouin zone in the energy range involving the pseudogap. It is found that the plane wave giving rise to the largest Fourier component always resonates with the {330} and {411} zone planes to produce the pseudogap near E_F. Moreover, a single-branch energy dispersion relation was constructed in the extended zone scheme by averaging the wave vector 2(k+G) having the largest Fourier component of the FLAPW wave function over selected electronic states in the Brillouin zone. The e/a value thus deduced is found to be close to 21/13 = 1.615 for Cu_5Zn_8, Cu_9Al_4, Ni_2Zn_, and Pd_2Zn_ γ brasses but to be only 1.4 and 1.3 for Co_2Zn_ and Fe_2Zn_, respectively