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Chapter 1. Introduction, perspectives, and aims. On the science of simulation and modelling. Modelling at bulk, meso, and nano scale. (2 hours). Chapter.

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Presentation on theme: "Chapter 1. Introduction, perspectives, and aims. On the science of simulation and modelling. Modelling at bulk, meso, and nano scale. (2 hours). Chapter."— Presentation transcript:

1 Chapter 1. Introduction, perspectives, and aims. On the science of simulation and modelling. Modelling at bulk, meso, and nano scale. (2 hours). Chapter 2. Experimental Techniques in Nanotechnology. Theory and Experiment: Two faces of the same coin (2 hours). Chapter 3. Introduction to Methods of the Classic and Quantum Mechanics. Force Fields, Semiempirical, Plane-Wave pseudpotential calculations. (2 hours) Chapter 4. Introduction to Methods and Techniques of Quantum Chemistry, Ab initio methods, and Methods based on Density Functional Theory (DFT). (4 hours) Chapter 5. Visualization codes, algorithms and programs. GAUSSIAN; CRYSTAL, and VASP. (6 hours)

2 . Chapter 6. Calculation of physical and chemical properties of nanomaterials. (2 hours). Chapter 7. Calculation of optical properties. Photoluminescence. (3 hours). Chapter 8. Modelization of the growth mechanism of nanomaterials. Surface Energy and Wullf architecture (3 hours) Chapter 9. Heterostructures Modeling. Simple and complex metal oxides. (2 hours) Chapter 10. Modelization of chemical reaction at surfaces. Heterogeneous catalysis. Towards an undertanding of the Nanocatalysis. (4 hours)

3 Chapter 6. Calculation of physical and chemical properties of nanomaterials Lourdes Gracia y Juan Andrés Departamento de Química-Física y Analítica Universitat Jaume I Spain & CMDCM, Sao Carlos Brazil Sao Carlos, Novembro 2010

4 - High-pressure phase transitions in crystalline systems Applications in front-line research - Li Diffusion in Crystalline Systems - Two State Reactivity and heterogeneous catalysis

5 Computational and Theoretical Chemistry (CTC) Solid State Chemistry Structrural properties of ceramic materials. Substitution and doping processes. Adsorption processes on metal oxide surfaces. Electronic and optical properties of piezoelectric and catalytic materials.

6 Cooperation CTC Experimental work Characterization of chemical species of difficult experimental detection Prediction Interpretation

7 High Pressure EffectsChemicalReactivity Diffusion Processes crystalline structures - Compressibility (polyhedra, bonds) - polymorphism - reaction paths - activation barriers Atoms (C, Li) in metals and metal oxides - stationary points - reaction paths - crossing points PESs of different spin multiplicities

8 Properties : - Geometry optimization, macroscopic parameters: equations of state, B 0, e, n - Electronic properties: r, DOS, band structure, dE g /dP - Theoric vibrational spectra (Raman, IR), vibrational modes asignation, w, dw/dP. Methodology: Density Functional Theory (DFT) Periodic Models Programs: CRYSTAL, VASP Characterization of phase transition mechanisms Pressure effect

9 MgAl 2 O 4 METHODOLOGY CRYSTAL Program DFT (B3LYP) 8-511G*- Mg, Al 8-411G* -O POLYHEDRA ANALYSIS Optimización de la geometría Curva E T -V código GIBBS: Ecuación de Estado V 0, B 0, B 0 Pressure effect Physical Review B 66, (2002) L. Gracia, A. Beltrán, J. Andrés, R. Franco and J. M. Recio

10 AlO 6 Occuped octahedra AlO 6 MgO 4 Occuped tetraheda MgO 4 O 6 Unfilled octahedra O 6 (O 4 ) 1 (O 4 ) 2 Unfilled tetrahedra (O 4 ) 1 y (O 4 ) 2

11 MgO+ Al 2 O 3 P(GPa) 6050 G (kJ/mol) cubica tipo-ferrita tipo-titanita MgO y -Al 2 O 3 titanita ferrita cúbica ESTABILIDAD GLOBAL distancia Mg 2+ -O 2- empaquetamiento MgO y -Al 2 O 3 IC (Mg 2+ ) ortorrómbicascúbica COMPRESIBILIDADES LINEALES Al-O/Mg-O

12 CdGa 2 Se 4, CdCr 2 Se 4 Cúbic Fd3m Cd 2+ tetrahedra Cr 3+ octahedra Tetragonal I4 POLYHEDRA ANALYSIS CdCr 2 Se 4 CdGa 2 Se 4 B 0 (GPa) Exp Teor (no magnetic) (ferromagnetic) Journal of Physics: Condensed Matter 16, (2004). A. Waskowska. L. Gerward, J. Staun Olsen, M. Feliz, R. Llusar, L. Gracia, M. Marqués and J. M. Recio

13 Polymorphs of CO 2 CO 2 -I Pa3 CO 2 -III Cmca Programa VASP PAW (LDA) Análisis topológico (AIM) METHODOLOGY ESTRUCTURES J. Physics: Condensed Matter 16, s1263 (2004) L. Gracia, M. Marqués, A. Beltrán, A. Martín Pendás, and J. M. Recio

14 P I42d P4 2 /mnm CO 2 -V V 0 ( Å 3 ) B 0 (GPa) d C-O ( Å ) (2) 1.168(2) 1.265(2) 1.385(4) 1.385(4) 1.577(4) 1.679(2) Pa3 Cmca(1) Cmca(2) P I42d P4 2 /mnm Molecular to polymeric phase transition: CO 2

15 Punto crítico firma sentido químico máximo -3 nucleos Punto de silla -1 enlaces - / 2 (r) = 0 TEORÍA DE ATOMOS EN MOLECULAS (AIM) carácter y fuerza del enlace polar C=O con CO 2 -I y CO 2 -III (1) / 2 > 0 covalente C-O con CO 2 -V / 2 <0 Isocontornos de la laplaciana de CO 2 -III (2): Configuration T

16 J. Phys. Chem. B 110, (2006) TiO 2 polymorphs anatase brookite at 3.8 GPa rutile brookite at 6.2 GPa. A. Beltrán, L. Gracia and J. Andrés

17 Brookite Surfaces stabilities (010) < (110) < (100) the electronic structure: - direct band gap in all of them - minimum gap energy: (110) (100) Ti 5c Ti 4c Ti 5c [100] [010] [001] [010] [100] [001] [110] [001] (010) (110)

18 Journal of Physical Chemistry B 111, (2007). SnO 2 polymorphs Highest bulk moduli values of 293 (pyrite) and 322 GPa (fluorite) phases A. Beltrán, L. Gracia and J. Andrés

19 SnO 2 polymorphs The phase transition sequence is consistent with an increase of coordination number of the tin ions, from 6 in the first three phases to 6+2 in the pyrite phase, 7 in the ZrO2-type orthorhombic phase I, 8 in fluorite phase and 9 in cotunnite orthorhombic phase II.

20 a) CrVO 4,-type b) zircon c) scheelite TiSiO 4 B3LYP calculations (CRYSTAL06 program) Phys. Rev. B 80, (2009) L. Gracia, A. Beltrán and D. Errandonea enthalpy vs presión curve (CrVO 4 -type as reference) V t = [V 2 (P t )-V 1 (P t )] / V 1 (P t ) GPa volume change of 11.8% GPa volume reduction of 8.5%.

21 In scheelite the low frequency mode with < 0, T(B g ), suggest the possibility of a transition to the post-scheelite structure, fergusonite or wolframite

22 ThGeO 4 zircon scheelite fergusonite PBE calculations (VASP program) Physical Review B 80, (2009) D. Errandonea, R. S. Kumar, L. Gracia, A. Beltrán, S. N. Achary, and A. K. Tyagi

23 Computations: Zircon as the most stable to 2 GPa Scheelite P > 2 GPa Fergusonite (post-scheelite) at 31 Gpa XRD: Zircon Scheelite Fergusonite 11 GPa 26GPa Decompression fergusonite – scheelite: no histeresis zircon-scheelita: not reversible.

24 Bastide diagram for ABX 4 structures Dashed lines: evolution of the ionic radii ratio with pressure D. Errandonea, F.J. Manjón, Progress in Materials Science, 53, 711 (2008)

25 1.958 Anhydrite Scheelite Barite a b c Monazite CaSO 4

26 E-V curve Monazita Anhidrita Barita Scheelita AgMnO 4 Structureanhydritemonazitebaritescheelite B 0 (B 0 ) 67.7 (5.61) (4.28) 64.8 (6.94) 84.1 (5.86) (4.19) B 0 B Exp B 0 (B 0 ') 45 (-) (4.25) Exp B 0 Exp B (±21.4) H-P curve anhydrite monazite at P t 5 GPa, reduction of volum -2% at 5GPa monazite barite (and/or scheelite) at 8 GPa

27 SiO 2 polymorphs stihovite -cristobalite -cristobalite is 0.1 eV more stable than stishovite at P=0 transition as low as 0.5 GPa with a large volume collapse L. Gracia, J. Contreras-García, A. Beltrán and J. M. Recio High Press Res 29, (2009).

28 SiO 2 polymorphs The atomic displacements connecting both polymorphs can be described under a martensitic approach (collective and concerted movements of all the atoms) in terms of a transition path of P symmetry. The transition path is traced up using a normalized coordinate: x, that evolves continuously from 0 ( -cristobalite, c) to 1 (stishovite, s)

29 Experimental Study DAC Diamond Anvil Cell Sincrotrones ALBA Nuevos Beamlines dedicados a altas presiones (APS/ESRF/SPring8/Diamond/Soleil/ALBA) Electrones acelerados a una energía de 7 mil millones de electron-volts (7 GeV). Radiación sincrotrón: radiación electromagnética producida por partículas cargadas que se mueven a alta velocidad (una fracción apreciable de la velocidad de la luz) en un campo magnético. Ionización del aire producida por un haz de rayos X en un sincrotrón

30 Diffusion Procesess Structure Cleveage of adsorbates Catalysis Alteration Impurities in metals VASP Program Plane waves / GGA METHODOLOGY

31 tet1 tet2 oct2 tet1 Oct > Tet1 > Tet2 E(relative,eV): 0.00 > 0.41 > 0.52 E(relative,eV): 0.00 > 0.41 > 0.52 oct1 Stability of C in Pd(111) Unit cell R30º - subsurface interstices L. Gracia, M. Calatayud, J. Andrés, C. Minot and M. Salmeron Physical Review B 71, (-4) (2005).

32 oct y tet1 tet2 ts1 ts oct E (eV) Horizontal Diffusion tet1 tet2 oct oct1 7

33 To bulk Diffusion oct y ts1 ts2 E (eV) tet1 tet oct2 z 0.63 tet1 tet2 oct2 oct1 7

34 Li in WO 3 Maximum energy barrier Minimum energy path distortion d(O 1 -O 2 ) 2.65 Å without Li Å d(Li-O)= d(Li-W)=2.09 Å 4 O, 2 W Cell 2x2 Pm3m Electrochemical and Solid State Letters. 8, J21 (2005) L. Gracia, J. García Cañadas, G. García-Belmonte, A. Beltrán, J. Andrés and J. Bisquert

35 () experimental data of D J. () theoretical calculations Energy barrier variation with x Rect lines relation with c=1.55 (simulation) and 1.25 (experiment). Process more favorable for low doped systems

36 Intercalation and diffusion of Li: Li 1+x Ti 2 O 4 (spinel ) Phys Rev. B 77, (2008) M. Anicete-Santos, L. Gracia, A. Beltrán and J. Andrés Li diffusion processes from tetrahedral 8a sites to ctahedral 16c sites are thermodynamically favorable only in the compositions x >

37 Intercalation and diffusion of Li: Li 1+x Ti 2 O 4 (spinel ) Phys Rev. B 77, (2008) M. Anicete-Santos, L. Gracia, A. Beltrán and J. Andrés

38 Chemical Reactivity R P TS R P PC R TS P R P PC TS R R P P PC Program GAUSSIAN DFT (B3LYP) 6-311G(2d,p) Vibrational Analysis IRC METHODOLOGY MECP by Harvey et al. E i y q EiEi Gradients Parallel to SEPs ortogonal to CP IRCs by Yoshizawa et al. IRC minimum TS closer Single-point energy calculation with the other spin electronic state geometries

39 V(OH) C 3 H 4 VO + + CO(CH 3 ) 2 / CHOC 2 H 5 C3H6C3H6 + VO 2 + VO + + CHOCH 3 C2H4C2H4 + V(OH) C 2 H 4 VO + + H 2 O + C 2 H 4 C2H6C2H6 + NbO H 2 O + O 2 MO(H 2 O) + M(OH) 2 + M=(V, Nb, Ta) Reaction mechanisms Spin inversion processes crossing points Topological analysis of electron density NbO H 2 O

40 VO C 2 H 4 VO + + CHOCH 3 J. Phys. Chem. A 107, 3107 (2003) L. Gracia, J. R. Sambrano, V. S. Safont, M. Calatayud, A, Beltrán and J. Andrés

41 t-VO + + s-H 2 O + s-C 2 H 4 s-VO + + s-H 2 O + s-C 2 H s-1 t-1 s-TS1/2 s-TS2/3 t-TS2/3 t-TS1/2 s-3 s-2 t-2 t-4 t-TS3/4 s-TS3/4 t-3 s-4 s-5 s-6 t-6 t-TS5 s-TS5 t-5 G (kcal/mol) 7.3 t-VO s-C 2 H 6 s-VO 2 + s-C 2 H 6 CP + VO C 2 H 6 VO + + H 2 O + C 2 H 4 V(OH) C 2 H 4 s-V(OH) s-C 2 H 4 t-V(OH) s-C 2 H 4 Organometallics 23, 730 (2004). Gracia, J. Andrés, J. R. Sambrano, V. S. Safont, and A. Beltrán

42 CP VO C 3 H 6 V(OH) C 3 H 4 VO + + CO( CH 3 ) 2 CHOC 2 H 5 Organometallics 25, 1643 (2006) L. Gracia, J. R. Sambrano, J. Andrés and A. Beltrán

43 CP1 CP2 NbO 3 - ( 1 A 1 )+ H 2 O + O 2 ( 3 g ) NbO 5 - ( 1 A)+ H 2 O J. Phys. Chem. A 108, (2004) R. Sambrano, L. Gracia, J. Andrés, S. Berski and A. Beltrán

44 Oxidation of Methanol to Formaldehyde on a Hydrated Vanadia Cluster P. González-Navarrete, L. Gracia, M. Calatayud and J. Andrés J Comput Chem 31, (2010). The main effect of hydration can be associated to the destabilization of the methoxy-intermediates five-fold V

45 Two intermediates, a five-fold coordinate and a tetrahedral vanadium, have been considered with C-H bond breaking barriers of 23.6 kcal/mol and 45.3 kcal/mol respectively. The penta-coordinate species, although it is 11.5 kcal/mol less stable than the tetrahedral one, might be regarded as a potential reactive intermediate Modelo Hidratado Actividad investigadora: Resultados tetrahedral V

46 on V-O-Ti Int4 on V-O-Ti TS on V=O TS V-O-Ti site leads to lower barrier, more stable dissociation product Int1 Int4 on V=O Int1 P. González-Navarrete, L. Gracia, M. Calatayud and J. Andrés J. Phys. Chem. C, Vol. 114, No. 13, 2010 The vanadia/titania catalysts

47 Comparison between both B3LYP/6-311G(2d,p) energy profiles. Path1 and Path2. a Broken-symmetry transition states and projected energies. b Triplet intermediates.


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