Averaging the intensity of many-layered structures for accurate stacking-fault analysis using Rietveld refinement

Many technologically important synthetic and natural materials display stacking faults which lead to complex peak broadenings, asymmetries and shifts in their powder diffraction patterns. The patterns can be described using an enlarged unit cell (called a supercell) containing an explicit description of the layers. Since the supercell can contain hundreds of thousands of atoms with hundreds of thousands of hkl reflections, a Rietveld approach has been too computationally demanding for all but the simplest systems. This article describes the implementation of the speed-ups necessary to allow Rietveld refinement in the computer program TOPAS Version 6 (Bruker AXS, Karlsruhe, Germany). Techniques implemented include: a peaks buffer that allows hundreds of thousands of hkl-dependent peak shapes to be automatically approximated by a few hundred peaks; an averaging process for hundreds of large supercells with minimum impact on computational time; a smoothing technique that allows for the use of small supercells which approximate supercells ten to 20 times larger; and efficient algorithms for stacking sequence generation. The result is Rietveld refinement of supercells operating at speeds several thousand times faster than traditional Rietveld refinements. This allows quantitative and simultaneous analysis of structure and microstructure in complex stacking-faulted samples

3D Modelling of Large Urban Scenes from Diverse Sources of Information

The complex and extensive nature of urban environments creates difficulties to the task of generating virtual models. Thus a great effort in terms of human resources, time and money is needed. Nevertheless a large number of professionals and institutions devout efforts to gather and analyse data from these urban environments. As data is usually stored in a digital format, it becomes a valuable asset to incorporate it in the modelling process of virtual environments. This paper presents a three-dimensional modelling system with interoperable access to data in diverse formats and digital support, drived by an L-system based modelling process that automatically generates initial solutions for virtual environments, which can be incrementally improved

Magnetoresistivity As A Probe To The Field-induced Change Of Magnetic Entropy In R Al2 Compounds (r=pr,nd,tb,dy,ho,er)

The heat capacity CP (T) of the ferromagnetic compounds R Al2 (R=Pr,Nd,Tb,Dy,Ho,Er) was measured at zero and applied magnetic field of 5 T in the temperature interval from 2 to 200 K. From these results are calculated the magnetic component of the entropy change, -Δ Smag (T) =S (0,T) -S (H,T). From resistivity measurements, ρ (H,T), from 2 to 300 K in the same compounds, we calculated the resistivity change due to the applied magnetic field, -Δ ρmag (T) = [ρmag (0,T) - ρmag (H,T)]. The results are compared and we observed a similar dependence between -Δ ρmag (T) and (T/ TC) m Δ Smag (T) with m=0 for T≥ TC and m=1 for T≤ TC. A simple model using a Hamiltonian considering molecular and crystalline electric fields, in a mean field approximation, is adopted for the calculus. Our results show that theory and experiment are in good agreement showing that the magnetoresistivity is a probe to the field-induced change of magnetic entropy in these compounds and can be extended to other materials. A model for the factor connecting both quantities, -Δ Smag (T) and -Δ ρmag (T), is developed. This factor contains mainly the effective exchange integral which is related to Fermi energy that in turn is related to the electron effective mass. © 2006 The American Physical Society.7413Ziman, M., (1972) Electrons and Phonons, , Oxford University Press, LondonPurwins, H.G., Leson, A., (1990) Adv. Phys., 39, p. 309. , ADPHAH 0001-8732 10.1080/00018739000101511Pecharsky, V.K., Gschneidner Jr., K.A., Pecharsky, A.O., Tishin, A.M., (2001) Phys. Rev. B, 64, p. 144406. , PRBMDO 0163-1829 10.1103/PhysRevB.64.144406Potter, H.H., (1932) Philos. Mag., Suppl., 13, p. 233. , ADPHAH 0001-8732Alexander, S., Helman, J.S., Balberg, I., (1976) Phys. Rev. B, 13, p. 304. , PLRBAQ 0556-2805 10.1103/PhysRevB.13.304Potter, H.H., (1931) Proc. R. Soc. London, Ser. a, 132, p. 560. , PRLAAZ 1364-5021Ravishankar, K., Sablik, M.J., Levy, P.M., Uffer, L.F., (1974) AIP Conf. Proc., 18, p. 923. , APCPCS 0094-243XVan Daal, H.J., Buschow, K.H.J., (1969) Solid State Commun., 7, p. 217. , SSCOA4 0038-1098Inoue, T., Sankar, S.G., Craig, R.S., Wallace, W.E., Gschneidner Jr., K.A., (1977) J. Phys. Chem. Solids, 38, p. 487. , JPCSAW 0022-3697Deenadas, C., Thompson, A.W., Craig, R.S., Wallace, W.E., (1971) J. Phys. Chem. Solids, 32, p. 1853. , JPCSAW 0022-3697Ibarra, M.R., Lee, E.W., Del Moral, A., Moze, O., (1985) Solid State Commun., 53, p. 183. , SSCOA4 0038-1098Ibarra, M.R., Moze, O., Algarabel, P.A., Arnaudas, J.I., Abell, J.S., Del Moral, A., (1988) J. Phys. C, 21, p. 2735. , JPSOAW 0022-3719Griffiths, R.B., (1969) Phys. Rev., 188, p. 942. , PHRVAO 0031-899X 10.1103/PhysRev.188.942Dekker, A.J., (1965) J. Appl. Phys., 36, p. 906. , JAPIAU 0021-8979 10.1063/1.1714260Von Ranke, P.J., Pecharsky, V.K., Gschneidner Jr., K.A., (1998) Phys. Rev. B, 58, p. 12110. , PRBMDO 0163-1829 10.1103/PhysRevB.58.12110Christen, M., (1980) Solid State Commun., 36, p. 571. , SSCOA4 0038-1098Sablik, M.J., Pureur, P., Creuzet, G., Fert, A., Levy, P.M., (1983) Phys. Rev. B, 28, p. 3890. , PRBMDO 0163-1829 10.1103/PhysRevB.28.3890Furrer, A., Purwins, H.G., (1977) Phys. Rev. B, 16, p. 2131. , PLRBAQ 0556-2805 10.1103/PhysRevB.16.2131Tsai, T.H., Sellmyer, D.J., (1979) Phys. Rev. B, 20, p. 4577. , PRBMDO 0163-1829 10.1103/PhysRevB.20.4577Milchberg, H.M., Freeman, R.R., Davey, S.C., More, R.M., (1988) Phys. Rev. Lett., 61, p. 2364. , PRLTAO 0031-9007 10.1103/PhysRevLett.61.2364Rawat, R., Das, I., (2001) J. Phys.: Condens. Matter, 13, p. 379. , JCOMEL 0953-8984 10.1088/0953-8984/13/19/104Das, I., Rawat, R., (2000) Solid State Commun., 115, p. 207. , SSCOA4 0038-1098Xiong, C.M., Sun, J.R., Chen, Y.F., Shen, B.G., Du, J., Li, Y.X., (2005) IEEE Trans. Magn., 41, p. 122. , IEMGAQ 0018-946

Isothermal Variation Of The Entropy (Δ St) For The Compound Gd5 Ge4 Under Hydrostatic Pressure

In the present work, the isothermal variation of the entropy (Δ ST) for the compound Gd5 Ge4 was studied at different applied hydrostatic pressures (from 0 up to 0.58 GPa). In all pressure ranges, we observe the giant magnetocaloric effect. The Δ ST data for the compound Gd5 Ge4 at zero applied pressure present two peaks: the lowest temperature peak is due to irreversible processes and the highest temperature peak is due to magnetostructural transitions. Increasing the pressure, the lowest temperature peak displaces to lower temperatures and disappears. The magnitude of the other peak has a nonlinear behavior with pressure. Different protocols were used to obtain Δ ST at zero applied pressure and the results indicate that Δ ST strongly depends on the initial and final states of Gd5 Ge4 compound. We also present a T-P magnetic phase diagram built from the available magnetic data. © 2008 American Institute of Physics.1046Pecharsky, V.K., Gschneidner Jr., K.A., (1999) J. Magn. Magn. Mater., 200, p. 44. , 0304-8853 10.1016/S0304-8853(99)00397-2Tishin, A.M., Spichkin, Y.I., (2003) The Magnetocaloric Effect and Its Applications, , (IOP, Bristol)Pecharsky, V.K., Gschneidner Jr., K.A., (1997) Phys. Rev. Lett., 78, p. 4494. , 0031-9007 10.1103/PhysRevLett.78.4494Magen, C., Arnold, Z., Morellon, L., Skorokhod, Y., Algarabel, P.A., Ibarra, M.R., Kamarad, J., (2003) Phys. Rev. Lett., 91, p. 207202. , 0031-9007 10.1103/PhysRevLett.91.207202Levin, E.M., Gschneidner Jr., K.A., Pecharsky, V.K., (2002) Phys. Rev. B, 65, p. 214427. , 0163-1829 10.1103/PhysRevB.65.214427Levin, E.M., Pecharsky, V.K., Gschneidner Jr., K.A., Miller, G.J., (2001) Phys. Rev. B, 64, p. 235103. , 0163-1829 10.1103/PhysRevB.64.235103Tang, H., Pecharsky, V.K., Gschneidner Jr., K.A., (2004) Phys. Rev. B, 69, p. 064410. , 0163-1829 10.1103/PhysRevB.69.064410Chattopadhyay, M.K., Manekar, M.A., Pecharsky, A.O., Pecharsky, V.K., Gschneidner Jr., K.A., Moore, J., Perkins, G.K., Cohen, L.F., (2004) Phys. Rev. B, 70, p. 214421. , 0163-1829 10.1103/PhysRevB.70.214421Mudryk, Ya., Holm, A.P., Gschneidner Jr., K.A., Pecharsky, V.K., (2005) Phys. Rev. B, 72, p. 064442. , 0163-1829 10.1103/PhysRevB.72.064442Levin, E.M., Gschneidner Jr., K.A., Lograsso, T.A., Schlagel, D.L., Pecharsky, V.K., (2004) Phys. Rev. B, 69, p. 144428. , 0163-1829 10.1103/PhysRevB.69.144428Pecharsky, V.K., Gschneidner Jr., K.A., (1997) Appl. Phys. Lett., 70, p. 3299. , 0003-6951 10.1063/1.119206Nikitin, S.A., Myalikgulyev, G., Tishin, A.M., Annaorazov, M.P., Asatryan, K.A., Tyurin, A.L., (1990) Phys. Lett. A, 148, p. 363. , 0375-9601 10.1016/0375-9601(90)90819-APecharsky, V.K., Gschneidner Jr., K.A., (1999) J. Appl. Phys., 86, p. 565. , 0021-8979 10.1063/1.370767Carvalho, A.M.G., (2006), Ph.D. thesis, UNICAMPCarvalho, A.M.G., Alves, C.S., De Campos, A., Coelho, A.A., Gama, S., Gandra, F.C.G., Von Ranke, P.J., De Oliveira, N.A., (2005) J. Appl. Phys., 97, pp. 10M320. , 0021-8979 10.1063/1.1860932Gschneidner Jr., K.A., Pecharsky, V.K., (2000) Annu. Rev. Mater. Sci., 30, p. 387. , 0084-6600 10.1146/annurev.matsci.30.1.387Carvalho, A.M.G., Alves, C.S., Colucci, C.C., Bolanho, M.A., Coelho, A.A., Gama, S., Nascimento, F.C., Cardoso, L.P., (2007) J. Alloys Compd., 432, p. 11. , 0925-8388 10.1016/j.jallcom.2006.05.121Wood, M.E., Potter, W.H., (1985) Cryogenics, 25, p. 667. , 0011-2275 10.1016/0011-2275(85)90187-0Magnus, A., Carvalho, G., Coelho, A.A., Gama, S., Von Ranke, P.J., De Oliveira, N.A., Da Silva, L.M., Gandra, F.C.G., (submitted

Causal Analysis of Some Biological Data for Illex illecebrosus from the Scotian Shelf

The method of path analysis is applied to data on the biology of the short-finned squid (Illex illecebrosus) from the Scotian Shelf. The variables considered in the analysis are catch, size, maturity, feeding, temperature and month. Four hypothesized causal models of the interrelationships of thesevariables are presented. Tamperature and month are shown to have a direct effect on catch-per-day as a measure of abundance, but they also have indirect effects through their action on the othervariables. The method of path analysis provides a framework forexplicitly examining hypotheses with respect to available data. More widespread application of the method to fisheries data seems warranted

Electron Spin Resonance G Shift In Gd5 Si4, Gd5 Ge4, And Gd5.09 Ge2.03 Si1.88

Gd5 Si4, Gd5 Ge4, and Gd5.09 Ge2.03 Si1.88 compounds were studied by electron spin resonance. The arc-melted samples were initially characterized by optical metallography, x-ray diffraction, and static magnetization measurements. The electron spin resonance results show a negative paramagnetic g shift for Gd5 Si4 and Gd5.09 Ge2.03 Si1.88, and a smaller positive one for Gd5 Ge4. The values of the exchange parameter (j) between the localized Gd-4f spins and the conduction electrons are obtained from the g shifts. These values are positive and of the same order of magnitude for Gd5 Si4 and Gd5.09 Ge2.03 Si1.88, and negative one order of magnitude smaller for Gd5 Ge4. The electron spin resonance data were interpreted considering the strongly bottlenecked solution of the coupled Bloch-Hasegawa equations. © 2006 The American Physical Society.7314Pecharsky, V.K., Gschneidner Jr., K.A., (1997) Phys. Rev. Lett., 78, p. 4494. , PRLTAO 0031-9007 10.1103/PhysRevLett.78.4494Pecharsky, V.K., Gschneidner Jr., K.A., (1997) J. Alloys Compd., 260, p. 98. , JALCEU 0925-8388 10.1016/S0925-8388(97)00143-6Choe, W., Pecharsky, V.K., Pecharsky, A.O., Gschneidner Jr., K.A., Young Jr., V.G., Miller, G.J., (2000) Phys. Rev. Lett., 84, p. 4617. , PRLTAO 0031-9007 10.1103/PhysRevLett.84.4617Levin, E.M., Pecharsky, V.K., Gschneidner Jr., K.A., (2000) Phys. Rev. B, 62, p. 14625. , PRBMDO 0163-1829 10.1103/PhysRevB.62.R14625Szade, J., Skorek, G., (1999) J. Magn. Magn. Mater., 196-197, p. 699. , JMMMDC 0304-8853Levin, E.M., Pecharsky, V.K., Gschneidner Jr., K.A., (1999) Phys. Rev. B, 60, p. 7993. , PRBMDO 0163-1829 10.1103/PhysRevB.60.7993Harmon, B.N., Antonov, V.N., (2002) J. Appl. Phys., 91, p. 9815. , JAPIAU 0021-8979 10.1063/1.1461896Levin, E.M., Pecharsky, V.K., Gschneidner Jr., K.A., Miller, G.J., (2001) Phys. Rev. B, 64, p. 235103. , PRBMDO 0163-1829 10.1103/PhysRevB.64.235103Skorek, G., Deniszczyk, J., Szade, J., (2002) J. Phys.: Condens. Matter, 14, p. 7273. , JCOMEL 0953-8984 10.1088/0953-8984/14/30/316Samolyuk, G.D., Antropov, V.P., (2002) J. Appl. Phys., 91, p. 8540. , JAPIAU 0021-8979 10.1063/1.1455614Pecharsky, V.K., Samolyuk, G.D., Antropov, V.P., Pecharsky, A.O., Gschneidner Jr., K.A., (2003) Solid State Chem., 171, p. 57. , 29CBA6Pires, M.J.M., Magnus Carvalho G, A., Gama, S., Da Silva, E.C., Coelho, A.A., Mansanares, A.M., (2005) Phys. Rev. B, 72, p. 224435. , PRBMDO 0163-1829 10.1103/PhysRevB.72.224435Gama, S., Alves, C.S., Coelho, A.A., Ribeiro, C.A., Persiano, A.I.C., Silva, D., (2004) J. Magn. Magn. Mater., 272-276, p. 848. , JMMMDC 0304-8853Usenko, N.I., Ivanov, M.I., Berezutski, V.V., Polotska, R.I., (1998) J. Alloys Compd., 266, p. 186. , JALCEU 0925-8388Zipper, E., (1982) J. Phys. F: Met. Phys., 12, p. 3123. , JPFMAT 0305-4608Glaunsinger, W.S., (1976) J. Phys. Chem. Solids, 37, p. 51. , JPCSAW 0022-3697 10.1016/0022-3697(76)90179-7Kaczmarska, K., (1996) J. Alloys Compd., 240, p. 88. , JALCEU 0925-8388Barnes, S.E., (1981) Adv. Phys., 30, p. 801. , ADPHAH 0001-8732 10.1080/00018738100101447Taylor, R.H., Coles, B.R., (1975) J. Phys. F: Met. Phys., 5, p. 121. , JPFMAT 0305-4608 10.1088/0305-4608/5/1/017Kaczmarska, K., Kwapulińska, E., Lebarski, A., Zipper, E., Chelkowski, A., (1985) J. Magn. Magn. Mater., 50, p. 101. , JMMMDC 0304-8853Schütz, G., Knülle, M., Wienke, R., Wilhelm, W., Wagner, W., Kienle, P., Frahm, R., (1988) Z. Phys. B: Condens. Matter, 73, p. 67. , ZPCMDN. 0722-3277. 10.1007/BF01312156Kim, J.W., Lee, Y., Wermeille, D., Sieve, B., Tan, L., Bud'Ko, S.L., Law, S., Goldman, A.I., (2005) Phys. Rev. B, 72, p. 064403. , PRBMDO 0163-1829 10.1103/PhysRevB.72.064403Lee, Y., Kim, J.W., Goldman, A.I., Harmon, B.N., (2005) J. Appl. Phys., 97, pp. 10A311. , JAPIAU 0021-8979 10.1063/1.185221

Calculation Of The Giant Magnetocaloric Effect In The Mnfep 0.45as0.55 Compound

We report the theoretical investigations on the giant magnetocaloric compound MnFeP0.45As0.55. The magnetic state equation used takes into account the magnetoelastic effect that leads the magnetic system to order under first order paramagnetic-ferromagnetic phase transition. The model parameters were determined from the magnetization data adjustment and used to calculate the magnetocaloric thermodynamic quantities. The theoretical calculations are compared with the available experimental data.709944101-094410-5Yu, B.F., Gao, Q., Zhang, B., Mang, X.Z., Chen, Z., (2003) Int. J. Refrig., 26, p. 622Gschneidner Jr., K.A., Pecharsky, V.K., (1997) Rare Earths: Science, Technology and Application III, , edited by R. C. Bautista, C. O. Bounds, T. W. Ellis, and B. T. Kilbourn The Minerals, Metals & Materials Society, WarendaleBrown, G.V., (1976) J. Appl. Phys., 47, p. 3673Pecharsky, V.K., Gschneidner Jr., K.A., (1997) Phys. Rev. Lett., 78, p. 4494Tegus, O., Brück, E., Buschow, K.H.J., De Boer, F.R., (2002) Nature, 415, p. 150. , LondonMorellon, L., Algarabel, P.A., Ibarra, M.R., Blasco, J., García-Landa, B., Arnold, Z., Albertini, F., (1998) Phys. Rev. B, 58, pp. R14721Rodbell, D.S., (1961) Phys. Rev. Lett., 7, p. 1Bean, C.P., Rodbell, D.S., (1961) Phys. Rev., 126, p. 104Bacmann, M., Soubeyroux, J.-L., Barrett, R., Fruchart, D., Zach, R., Niziol, S., Fruchart, R., (1983) J. Magn. Magn. Mater., 134, p. 59Brück, E., Tegus, O., Li, X.W., Deboer, F.R., Buschow, K.H.J., (2003) Physica B, 327, p. 431Tegus, O., Brück, E., Zhang, L., Dagula, Buschow, K.H.J., De Boer, F.R., (2002) Physica B, 319, p. 174Zach, R., Guillot, M., Tobola, J., (1998) J. Appl. Phys., 83, p. 7237Tegus, O., (2003) Novel Materials for Magnetic Refrigeration, , PhD thesis, Van der Waals-Zeeman Instituut, Universiteit van Amsterdam, Printer Partners Ipskamp B. V., ISBN: 9057761076, OctoberVon Ranke, P.J., Grangeia, D.F., Caldas, A., De Oliveira, N.A., (2003) J. Appl. Phys., 93, p. 4055Wada, H., Tanabe, Y., (2001) Appl. Phys. Lett., 79, p. 3302Wada, H., Morikawa, T., Taniguchi, K., Shibata, T., Yamada, Y., Akishige, Y., (2003) Physica B, 328, p. 11