A DFT study of structural, dynamical properties and quasiparticle band structure of solid nitromethane

We report a detailed theoretical study of the structural, vibrational, and optical properties of solid nitromethane using first principles density functional calculations. The ground state properties were calculated using a plane wave pseudopotential code with either the local density approximation (LDA), the generalized gradient approximation (GGA), or with a correction to include van derWaals interactions. Our calculated equilibrium lattice parameters and volume using a dispersion correction are found to be in reasonable agreement with the experimental results. Also, our calculations reproduce the experimental trends in the structural properties at high pressure. It was found to be a discontinuity in the bond length, bond angles and also a weaking of hydrogen bond strength in the pressure range from 10 to 12 GPa, picturing the structural transition from phase I to Phase II. Moreover, we predict the elastic constants of solid nitromethane and found that the corresponding bulk modulus is in good agreement with experiments. The calculated elastic constants are showing an order of C11> C22 > C33, indicating that the material is more compressible along the c-axis. We also calculated the zone center vibrational frequencies and discuss the internal and external modes of this material under pressure. From this, we found the softing of lattice modes around 8 to 12 GPa. We have also attempt the quasiparticle band structure of solid nitromethane with the G0W0 approximation and found that nitromethane is an indirect band gap insulator with a value of the band gap of about 7.8 eV with G0W0 approximation. Finally, the optical properties of this material, namely the absorptive and dispersive part of the dielectric function, and the refractive index and absorption spectra are calculated and the contribution of different transition peaks of the absorption spectra are analyzed.Comment: 12 pages, 9 figure

Correlated Electrons Step-by-Step: Itinerant-to-Localized Transition of Fe Impurities in Free-Electron Metal Hosts

High-resolution photoemission spectroscopy and realistic ab-initio calculations have been employed to analyze the onset and progression of d-sp hybridization in Fe impurities deposited on alkali metal films. The interplay between delocalization, mediated by the free-electron environment, and Coulomb interaction among d-electrons gives rise to complex electronic configurations. The multiplet structure of a single Fe atom evolves and gradually dissolves into a quasiparticle peak near the Fermi level with increasing the host electron density. The effective multi-orbital impurity problem within the exact diagonalization scheme describes the whole range of hybridizations.Comment: 10 pages, 4 figure

Probing The Electronic Structure Of Pure And Doped Cem In5 (m=co,rh,ir) Crystals With Nuclear Quadrupolar Resonance

We report calculations of the electric-field gradients (EFGs) in pure and doped CeM In5 (M=Co, Rh, and Ir) compounds and compare with experiment. The degree to which the Ce4f electron is localized is treated within various models: the local-density approximation, generalized gradient approximation (GGA), GGA+U, and 4f -core approaches. We find that there is a correlation between the observed EFG and whether the 4f electron participates in the band formation or not. We also find that the EFG evolves linearly with Sn doping in CeRhIn5, suggesting the electronic structure is modified by doping. In contrast, the observed EFG in CeCoIn5 doped with Cd changes little with doping. These results indicate that nuclear quadrupolar resonance is a sensitive probe of electronic structure. © 2008 The American Physical Society.7724Slichter, C.P., (1990) Principles of Magnetic Resonance, , 3rd ed. (Springer-Verlag, New YorkCurro, N.J., Caldwell, T., Bauer, E.D., Morales, L.A., Graf, M.J., Bang, Y., Balatsky, A.V., Sarrao, J.L., (2005) Nature (London), 434, p. 622. , NATUAS 0028-0836 10.1038/nature03428Farnan, I., Cho, H., Weber, W.J., (2007) Nature (London), 445, p. 190. , NATUAS 0028-0836 10.1038/nature05425Zheng, G.-Q., Tanabe, K., Mito, T., Kawasaki, S., Kitaoka, Y., Aoki, D., Haga, Y., Onuki, Y., (2001) Phys. Rev. Lett., 86, p. 4664. , PRLTAO 0031-9007 10.1103/PhysRevLett.86.4664Movshovich, R., Jaime, M., Thompson, J.D., Petrovic, C., Fisk, Z., Pagliuso, P.G., Sarrao, J.L., (2001) Phys. Rev. Lett., 86, p. 5152. , PRLTAO 0031-9007 10.1103/PhysRevLett.86.5152Pagliuso, P.G., Petrovic, C., Movshovich, R., Hall, D., Hundley, M.F., Sarrao, J.L., Thompson, J.D., Fisk, Z., (2001) Phys. Rev. B, 64, p. 100503. , PRBMDO 0163-1829 10.1103/PhysRevB.64.100503Zapf, V.S., Freeman, E.J., Bauer, E.D., Petricka, J., Sirvent, C., Frederick, N.A., Dickey, R.P., Maple, M.B., (2001) Phys. Rev. B, 65, p. 014506. , PRBMDO 0163-1829 10.1103/PhysRevB.65.014506Ormeno, R.J., Sibley, A., Gough, C.E., Sebastian, S., Fisher, I.R., (2002) Phys. Rev. Lett., 88, p. 047005. , PRLTAO 0031-9007 10.1103/PhysRevLett.88.047005Park, T., Ronning, F., Yuan, H.Q., Salamon, M.B., Movshovich, R., Sarrao, J.L., Thompson, J.D., (2006) Nature (London), 440, p. 65. , NATUAS 0028-0836 10.1038/nature04571Petrovic, C., Movshovich, R., Jaime, M., Pagliuso, P.G., Hundley, M.F., Sarrao, J.L., Fisk, Z., Thompson, J.D., (2001) Europhys. Lett., 53, p. 354. , EULEEJ 0295-5075 10.1209/epl/i2001-00161-8Bao, W., Pagliuso, P.G., Sarrao, J.L., Thompson, J.D., Fisk, Z., Lynn, J.W., Erwin, R.W., (2000) Phys. Rev. B, 62, p. 14621. , PRBMDO 0163-1829 10.1103/PhysRevB.62.R14621Curro, N.J., Hammel, P.C., Pagliuso, P.G., Sarrao, J.L., Thompson, J.D., Fisk, Z., (2000) Phys. Rev. B, 62, p. 6100. , PRBMDO 0163-1829 10.1103/PhysRevB.62.R6100Hegger, H., Petrovic, C., Moshopoulou, E.G., Hundley, M.F., Sarrao, J.L., Fisk, Z., Thompson, J.D., (2000) Phys. Rev. Lett., 84, p. 4986. , PRLTAO 0031-9007 10.1103/PhysRevLett.84.4986Shishido, H., Settai, R., Araki, S., Ueda, T., Inada, Y., Kobayashi, T.C., Muramatsu, T., Onuki, Y., (2002) Phys. Rev. B, 66, p. 214510. , PRBMDO 0163-1829 10.1103/PhysRevB.66.214510Shishido, H., Settai, R., Harima, H., Onuki, Y., (2005) J. Phys. Soc. Jpn., 74, p. 1103. , JUPSAU 0031-9015 10.1143/JPSJ.74.1103Pham, L.D., Park, T., Maquilon, S., Thompson, J.D., Fisk, Z., (2006) Phys. Rev. Lett., 97, p. 056404. , PRLTAO 0031-9007 10.1103/PhysRevLett.97.056404Daniel, M., Bauer, E.D., Han, S.-W., Booth, C.H., Cornelius, A.L., Pagliuso, P.G., Sarrao, J.L., (2005) Phys. Rev. Lett., 95, p. 016406. , PRLTAO 0031-9007 10.1103/PhysRevLett.95.016406Paglione, J., Sayles, T.A., Ho, P.-C., Jeffries, J.R., Maple, M.B., (2007) Nat. Phys., 3, p. 703. , ZZZZZZ 1745-2473Urbano, R.R., Young, B.-L., Curro, N.J., Thompson, J.D., Pham, L.D., Fisk, Z., (2007) Phys. Rev. Lett., 99, p. 146402. , PRLTAO 0031-9007 10.1103/PhysRevLett.99.146402Czyzyk, M.T., Sawatzky, G.A., (1994) Phys. Rev. B, 49, p. 14211. , PRBMDO 0163-1829 10.1103/PhysRevB.49.14211Anisimov, V.I., Solovyev, I.V., Korotin, M.A., Czyzyk, M.T., Sawatzky, G.A., (1993) Phys. Rev. B, 48, p. 16929. , PRBMDO 0163-1829 10.1103/PhysRevB.48.16929Bianchi, A., Movshovich, R., Vekhter, I., Pagliuso, P.G., Sarrao, J.L., (2003) Phys. Rev. Lett., 91, p. 257001. , PRLTAO 0031-9007 10.1103/PhysRevLett.91.257001Blaha, P., Schwarz, K., Madsen, G.K.H., Kvasnicka, D., Luitz, J., (2001) WIEN2k, An Augmented Plane Wave + Local Orbitals Program for Calculating Crystal Properties, , Karlheinz Schwarz, Techn. Universität Wien, AustriaKuneš, J., Novák, P., Divis, M., Oppeneer, P.M., (2001) Phys. Rev. B, 63, p. 205111. , PRBMDO 0163-1829 10.1103/PhysRevB.63.205111Blaha, P., Schwarz, K., Herzig, P., (1985) Phys. Rev. Lett., 54, p. 1192. , PRLTAO 0031-9007 10.1103/PhysRevLett.54.1192Herzig, P., (1985) Theor. Chim. Acta, 67, p. 323. , TCHAAM 0040-5744 10.1007/BF00529304Mohn, P., (2000) Hyperfine Interact., 128, p. 67. , HYINDN 0304-3843 10.1023/A:1012619212656Petrovic, C., Pagliuso, P.G., Hundley, M.F., Movshovich, R., Sarrao, J.L., Thompson, J.D., Fisk, Z., Monthoux, P., (2001) J. Phys.: Condens. Matter, 13, p. 337. , JCOMEL 0953-8984 10.1088/0953-8984/13/17/103Perdew, J.P., Wang, Y., (1992) Phys. Rev. B, 45, p. 13244. , PRBMDO 0163-1829 10.1103/PhysRevB.45.13244Perdew, J.P., Burke, K., Ernzerhof, M., (1996) Phys. Rev. Lett., 77, p. 3865. , PRLTAO 0031-9007 10.1103/PhysRevLett.77.3865Kohori, Y., Inoue, Y., Kohara, T., Tomka, G., Riedi, P.C., (1999) Physica B, 259-261, p. 103. , PHYBE3 0921-4526Rusz, J., Biasini, M., (2005) Phys. Rev. B, 71, p. 233103. , PRBMDO 0163-1829 10.1103/PhysRevB.71.233103Kohori, Y., Yamato, Y., Iwamoto, Y., Kohara, T., Bauer, E.D., Maple, M.B., Sarrao, J.L., (2001) Phys. Rev. B, 64, p. 134526. , PRBMDO 0163-1829 10.1103/PhysRevB.64.134526Curro, N.J., Simovic, B., Hammel, P.C., Pagliuso, P.G., Sarrao, J.L., Thompson, J.D., Martins, G.B., (2001) Phys. Rev. B, 64, p. 180514. , PRBMDO 0163-1829 10.1103/PhysRevB.64.180514Lynch, D.W., Weaver, J.H., (1987) Handbook on the Physics and Chemistry of Rare Earths, 10, p. 231. , edited by K. A. Gschneidner, L. Eyring, and S. Hüfner (North-Holland, AmsterdamShishido, H., Settai, R., Aoki, D., Ikeda, S., Nakawaki, H., Nakamura, N., Iizuka, T., Onuki, Y., (2002) J. Phys. Soc. Jpn., 71, p. 162. , JUPSAU 0031-9015 10.1143/JPSJ.71.162Elgazzar, S., Opahle, I., Hayn, R., Oppeneer, P.M., (2004) Phys. Rev. B, 69, p. 214510. , PRBMDO 0163-1829 10.1103/PhysRevB.69.214510Oppeneer, P.M., Elgazzar, S., Shick, A.B., Opahle, I., Rusz, J., Hayn, R., (2007) J. Magn. Magn. Mater., 310, p. 1684. , JMMMDC 0304-8853 10.1016/j.jmmm.2006.10.763Bauer, E.D., Capan, C., Ronning, F., Movshovich, R., Thompson, J.D., Sarrao, J.L., (2005) Phys. Rev. Lett., 94, p. 047001. , PRLTAO 0031-9007 10.1103/PhysRevLett.94.047001Nakatsuji, S., Pines, D., Fisk, Z., (2004) Phys. Rev. Lett., 92, p. 016401. , PRLTAO 0031-9007 10.1103/PhysRevLett.92.016401Curro, N.J., Young, B.-L., Schmalian, J., Pines, D., (2004) Phys. Rev. B, 70, p. 235117. , PRBMDO 0163-1829 10.1103/PhysRevB.70.235117Yashima, M., Kawasaki, S., Kawasaki, Y., Zheng, G.-Q., Kitaoka, Y., Shishido, H., Settai, R., Onuki, Y., (2004) J. Phys. Soc. Jpn., 73, p. 2073. , JUPSAU 0031-9015 10.1143/JPSJ.73.2073Kawasaki, S., Zheng, G.-Q., Kan, H., Kitaoka, Y., Shishido, H., Onuki, Y., (2005) Phys. Rev. Lett., 94, p. 037007. , PRLTAO 0031-9007 10.1103/PhysRevLett.94.037007Haase, J., Sushkov, O.P., Horsch, P., Williams, G.V.M., (2004) Phys. Rev. B, 69, p. 094504. , PRBMDO 0163-1829 10.1103/PhysRevB.69.094504Curro, N.J., Nicklas, M., Stockert, O., Park, T., Habicht, K., Kiefer, K., Pham, L.D., Thompson, J.D., Steglich, F., (2007) Phys. Rev. B, 76, p. 052401. , PRBMDO 0163-1829 10.1103/PhysRevB.76.052401Settai, R., Shishido, H., Ikeda, S., Murakawa, Y., Nakashima, M., Aoki, D., Haga, Y., Onuki, Y., (2001) J. Phys.: Condens. Matter, 13, p. 627. , JCOMEL 0953-8984 10.1088/0953-8984/13/27/103Normile, P.S., Heathman, S., Idiri, M., Boulet, P., Rebizant, J., Wastin, F., Lander, G.H., Lindbaum, A., (2005) Phys. Rev. B, 72, p. 184508. , PRBMDO 0163-1829 10.1103/PhysRevB.72.184508Oppeneer, P.M., (2001) Handbook of Magnetic Materials, 13, pp. 229-422. , edited by K. H. J. Buschow (Elsevier, AmsterdamOppeneer, P.M., Antonov, V.N., Yaresko, A.N., Perlov, A.Y., Eschrig, H., (1997) Phys. Rev. Lett., 78, p. 4079. , PRLTAO 0031-9007 10.1103/PhysRevLett.78.4079Shim, J.H., Haule, K., Kotliar, G., (2007) Science, 318, p. 1615. , SCIEAS 0036-8075 10.1126/science.1149064Alver, U., Goodrich, R.G., Harrison, N., Hall, D.W., Palm, E.C., Murphy, T.P., Tozer, S.W., Fisk, Z., (2001) Phys. Rev. B, 64, p. 180402. , PRBMDO 0163-1829 10.1103/PhysRevB.64.180402Christianson, A.D., Lawrence, J.M., Pagliuso, P.G., Moreno, N.O., Sarrao, J.L., Thompson, J.D., Riseborough, P.S., Lacerda, A.H., (2002) Phys. Rev. B, 66, p. 193102. , PRBMDO 0163-1829 10.1103/PhysRevB.66.193102Haga, Y., Inada, Y., Harima, H., Oikawa, K., Murakawa, M., Nakawaki, H., Tokiwa, Y., Onuki, Y., (2001) Phys. Rev. B, 63, p. 060503. , PRBMDO 0163-1829 10.1103/PhysRevB.63.060503Fujimori, S.-I., Fujimori, A., Shimada, K., Narimura, T., Kobayashi, K., Namatame, H., Taniguchi, M., Opnuki, Y., (2006) Phys. Rev. B, 73, p. 224517. , PRBMDO 0163-1829 10.1103/PhysRevB.73.224517Paglione, J., Tanatar, M.A., Hawthorn, D.G., Ronning, F., Hill, R.W., Sutherland, M., Taillefer, L., Petrovic, C., (2006) Phys. Rev. Lett., 97, p. 106606. , PRLTAO 0031-9007 10.1103/PhysRevLett.97.10660

Shape resonance for the anisotropic superconducting gaps near a Lifshitz transition: the effect of electron hopping between layers

The multigap superconductivity modulated by quantum confinement effects in a superlattice of quantum wells is presented. Our theoretical BCS approach captures the low-energy physics of a shape resonance in the superconducting gaps when the chemical potential is tuned near a Lifshitz transition. We focus on the case of weak Cooper-pairing coupling channels and strong pair exchange interaction driven by repulsive Coulomb interaction that allows to use the BCS theory in the weak-coupling regime neglecting retardation effects like in quantum condensates of ultracold gases. The calculated matrix element effects in the pairing interaction are shown to yield a complex physics near the particular quantum critical points due to Lifshitz transitions in multigap superconductivity. Strong deviations of the ratio $2\Delta/T_c$ from the standard BCS value as a function of the position of the chemical potential relative to the Lifshitz transition point measured by the Lifshitz parameter are found. The response of the condensate phase to the tuning of the Lifshitz parameter is compared with the response of ultracold gases in the BCS-BEC crossover tuned by an external magnetic field. The results provide the description of the condensates in this regime where matrix element effects play a key role.Comment: 12 pages, 6 figure

Organic Foulants Characteristics in Membrane Bioreactor

A laboratory scale side stream membrane bioreactor system with flat sheet membrane was operated for 5–days run at three different aeration rates (100, 200 and 300 L/h). The organic foulants deposited on the membrane surface was studied after extraction with 5% NaOH solution using three spectroscopic techniques. The IR spectra showed no distinct similarity in peaks among the three. The fluorescence spectra showed increase of soluble microbial products in foulant with decrease of aeration rate. This was supported by the size exclusion chromatography in which biopolymers concentration in fouling decreased with increasing aeration rate

On the Thermal Stability of Graphone

Molecular dynamics simulation is used to study thermally activated migration of hydrogen atoms in graphone, a magnetic semiconductor formed of a graphene monolayer with one side covered with hydrogen so that hydrogen atoms are adsorbed on each other carbon atom only. The temperature dependence of the characteristic time of disordering of graphone via hopping of hydrogen atoms to neighboring carbon atoms is established directly. The activation energy of this process is found to be Ea=(0.05+-0.01) eV. The small value of Ea points to extremely low thermal stability of graphone, this being a serious handicap for practical use of the material in nanoelectronics.Comment: 3 figure

Observation of Multi-Gap Superconductivity in GdO(F)FeAs by Andreev Spectroscopy

We have studied current-voltage characteristics of Andreev contacts in polycrystalline GdO$_{0.88}$F$_{0.12}$FeAs samples with bulk critical temperature ${T_c}$ = (52.5 \pm 1)K using break-junction technique. The data obtained cannot be described within the single-gap approach and suggests the existence of a multi-gap superconductivity in this compound. The large and small superconducting gap values estimated at T = 4.2K are {\Delta}L = 10.5 \pm 2 meV and {\Delta}S = 2.3 \pm 0.4 meV, respectively.Comment: 5 pages, 4 figures, submitted to JETP Letter

Pressure Study of Superconducting Oxypnictide LaFePO

Electrical resistivity and magnetic susceptibility measurements under high pressure were performed on an iron-based superconductor LaFePO. A steep increase in superconducting transition temperature (Tc) of LaFePO with dTc/dP > 4 K/GPa to a maximum of 8.8 K for P = 0.8 GPa was observed. These results are similar to isocrystalline LaFeAsO1-xFx system reported previously. X-ray diffraction measurements were also performed under high pressure up to 10 GPa, where linear compressibility ka and kc are presented.Comment: 11 pages, 4 figure