Documento PDF - UniCA Eprints - UniversitÃ degli studi di Cagliari.

More documents

Recommendations

Info

A.2 the force field 77Finally, τ too small produces unrealistical low temperaturefluctuations. A typical and efficient choice for τ is ∼ 100δt.The Nosé Hoover [117, 118] approach is an improvementof the Berendsen method in which an extra degree of freedoms is introduced. This new variable is associated witha "mass" Q that determines the coupling between the bathand the real system controlling the temperature fluctuations.a.1.4Periodic Boundary Conditions (PBC)In order to minimize the number of atoms in a simulationand to avoid surface effects, the Periodic BoundaryConditions (PBC) can be introduced. They allow to simulatea finite system in a cell periodically repeated in thethree directions of the space. Each particle interact with theother particles in the cell and with the others in the imagecells within the cutoff distance, thus simulating an infinitesystem.a.2 the force fieldThe critical requirement for MD is the choice of a suitablepotential that well describes the physical propertiesof the material of interest. Model Potential Molecular Dynamics(MPMD) makes use of empirical potentials, whoseparameters, obtained by experiments or ab initio calculations,are fitted to reproduce the physical properties of thesystem considered.Among the more common force fields there are AMBER[62], CHARMM [119], Gromos [120] and OPLS [26].In this work the calculation for the organic componentshave been performed by using the AMBER (Assisted ModelBuilding Refinement) force field, particular suitable for thestudy of organic materiasl. The Amber force field considerstwo kind of interactions: the bonded and the non-bonded[62].
78 molecular dynamicsa.2.1Bonded interactionThe bondend interactions involved three contributions[62]:U bonded = U bonds + U angles + U dihedrals(A.19)U bonds = ∑ 1 2 K b(r − r 0 ) 2 describes the energy betweencovalently bonded atoms. K b is the constant of the force, r 0is the equilibrium distance between two atoms and r is thelenght of the bond (Figure A.2 top left).U angle = ∑ 1 2 K a(θ − θ 0 ) 2 describes the energy due to thedeformation of the angle formed by the three particles. K ais the constant of the force and θ 0 is the equilibrium anglebetween the atoms and r is the lenght of the bond (FigureA.2 top right).U dihedral = ∑ 1 2 V φ(1 + cos(nφ − φ 0 ) represents the potentialdue to the torsion angles. The energy is linked at therotation around a bond. V φ is a constant that defines therotation barrier around the bond, φ 0 is the equilibrium dihedralangle and n is the multiplicity of the torsions (FigureA.2 bottom).Figure A.1.: Bonding (top left), angular (top right) and dihedral (bottom)interaction between two, three and four atoms.a.2.2Non-bonded interactionThe non-bonded interaction involves the atoms not chemicallybonded or separated by three o more bonds. It isthe sum between the Coulombic attraction and the van der
Page 1 and 2:
Università degli Studi di Cagliari
Page 4:
A C K N O W L E D G M E N T SI woul
Page 7 and 8:
example of a novel class of systems
Page 10 and 11:
C O N T E N T S1 introduction 11.1
Page 12 and 13:
L I S T O F F I G U R E SFigure 1.1
Page 14 and 15:
List of FiguresxiiiFigure 2.15 Init
Page 16 and 17:
List of FiguresxvFigure 4.6Figure 4
Page 18:
Figure 5.7Figure 5.8Figure A.1Figur
Page 21 and 22:
2 introduction1-3 eV) and the trans
Page 23 and 24:
4 introductionorder in such a compl
Page 25 and 26:
6 introductionprocesses that need t
Page 27 and 28:
8 introduction1.2 physical factors
Page 29 and 30:
10 introductionrecovered by the int
Page 31 and 32:
12 introductionA cheap and environm
Page 33 and 34:
14 introductiondensed phases [63, 7
Page 36 and 37:
P 3 H T - P O LY ( 3 - H E X Y LT H
Page 38 and 39:
2.1 mechanism of assembling and mor
Page 40 and 41:
2.2 p3ht assembling and intermolecu
Page 42 and 43:
2.3 p3ht crystalline bulk phases 23
Page 44 and 45:
2.5 nanocrystalline p3ht 25Figure 2
Page 46 and 47: 2.5 nanocrystalline p3ht 27Table 2.
Page 48 and 49: 2.6 conclusions 29Figure 2.13.: Ini
Page 50 and 51: P O LY M E R / S E M I C O N D U C
Page 52 and 53: 3.3 adhesion of a single p3ht molec
Page 54 and 55: 3.4 p3ht/zno interface 35surface (t
Page 56 and 57: 3.5 p3ht/zno interface: low deposit
Page 58 and 59: 3.6 p3ht/zno interface: high deposi
Page 64 and 65: 3.7 effective model for the transpo
Page 66 and 67: 3.8 conclusions 47As for the low te
Page 68 and 69: T E R N A RY Z N O / Z N P C / P 3
Page 70 and 71: 4.1 self assembling of znpcs on zno
Page 72 and 73: 4.2 polymer interaction with znpcs
Page 74 and 75: 4.3 electronic and optical properti
Page 76 and 77: 4.3 electronic and optical properti
Page 78 and 79: 4.4 conclusions 59ties. The absorpt
Page 80 and 81: I N T E R A C T I O N B E T W E E N
Page 82 and 83: 5.2 solvent thf interaction with zn
Page 88 and 89: 5.3 conclusions 69γ L/L ∼ 0.112
Page 90 and 91: C O N C L U S I O N SIn this thesis
Page 92 and 93: M O L E C U L A R D Y N A M I C SAa
Page 94 and 95: A.1 molecular dynamics 75a.1.2The t
Page 98 and 99: A.2 the force field 79Waals interac
Page 100 and 101: A.3 methods 81tional Theory (DFT) l
Page 102 and 103: B I B L I O G R A P H Y[1] http://w
Page 104 and 105: ibliography 85[17] J. D. Servaites,
Page 106 and 107: ibliography 87Zakeeruddin, and M. G
Page 108 and 109: ibliography 89Phys. Chem. Chem. Phy
Page 110 and 111: ibliography 91[65] D. J. Binks and
Page 112 and 113: ibliography 93cells,” Energy Envi
Page 114 and 115: ibliography 95[97] C. Ingrosso, A.
Page 116 and 117: ibliography 97298.15 k,” Journal
Page 118 and 119: ibliography 99charges. am1-bcc mode
Page 120: colophonThis document was typeset u
show all

Documento PDF - UniCA Eprints - UniversitÃ degli studi di Cagliari.

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?