Unit:
Department of PhysicsLibrary of the School of Science
Supervisors info:
ΚΩΝΣΤΑΝΤΙΝΟΣ ΣΙΜΣΕΡΙΔΗΣ, ΑΝΑΠΛΗΡΩΤΗΣ ΚΑΘΗΓΗΤΗΣ, ΤΜΗΜΑ ΦΥΣΙΚΗΣ, ΕΘΝΙΚΟ ΚΑΙ ΚΑΠΟΔΙΣΤΡΙΑΚΟ ΠΑΝΕΠΙΣΤΗΜΙΟ ΑΘΗΝΩΝ
Original Title:
Μεταβίβαση φορτίου σε δικυανοπολυΐνια (NC. . . CC. . .CN) με Ισχυρή Δέσμευση και RT-TDDFT
Translated title:
Charge transfer in dicyanopolyynes (NC. . . CC. . . CN) via Tight Binding and RT-TDDFT
Summary:
We investigate the hole (empty electron position) transfer in dicyanopolyynes, i.e. atomic
carbon and nitrogen nanowires, via Tight Binding and RT-TDDFT, using the programming and
computing platform named MATLAB and the open-source computer package named NWChem.
We study three molecules overall. The simplest one consists of four atoms (N=4) and
is called Cyanogen (C2N2), the medium one consists of six atoms (N=6) and is called 2-Butynedinitrile (C4N2) and the largest one consists of eight atoms (N=8) and is called Hexadiynedinitrile (C6N2). In Tight Binding (TB) we calculate the eigenenergies of the π structure
of the studied molecules, as well as the probability of finding the hole in relation to time in
every possible site of the molecule, the mean probability of the hole in every site, the dipole
moment in relation to time, the FFT of the dipole moment and the mean transfer rate of the
charge in all sites. In Density Functional Theory (DFT) we focus onto the basis sets 6-31G,
6-31G* and cc-pVDZ and also the B3LYP exchange and correlation functional. The procedure is divided into four stages: firstly we perform optimize the geometry of the atoms of the
molecule and afterwards we determine the energy of the ground state DFT alongside with the
Löwdin charge population analysis. Moreover, we investigate the vibrations of the molecule
and we evaluate the eigenfrequencies of the normal vibrational modes. Lastly, we study the
hole transfer longwise the one-dimensional nanowires on the static state of each molecule.
The hole is created on the first nitrogen atom of the chain, artificially, using Constrained
DFT (CDFT) and the Löwdin charge population analysis that we have already calculated.
Consequently, we examine the time progression of the system, calculating the charge of the
hole in every site of the molecule in relation to time, the dipole moment of the system and its
FFT. Each site is defined as each atom that constitute each molecule. Apart from the three
basic molecules of this thesis, we also perform the same four stages of DFT indicatively for
water using the basis sets 6-31G and 6-31++G**, in order to explain the whole procedure and
results obtained from it in more detail.
Eventually, we perform a comparison between the results of the two theories, TB and DFT,
focusing our interest on a few specific and basic physical quantities that explain hole transfer:
• Geometry optimization and atomic distances.
• Hole charge and probabilities of finding the charge carrier in relation to time.
• Dipole moment and its FFT, i.e. the set of frequencies of the major oscillations of the
dipole moment, along the axis of the molecules in relation to time.
• Mean charge transfer rates from one edge of the chain to the other and the mean probabilities of finding the hole in each site of the molecule.
Main subject category:
Science
Keywords:
TB, DFT, CDFT, TD-DFT, RT-TDDFT, Carbynes, Dicyanopolyynes, MATLAB, NWChem, Gaussian Type Basis Set, Geometry Optimization, Ground State DFT, Mulliken Population Analysis, Löwdin Population Analysis, FFT, Set of Frequencies, Nanowire, Hole, Charge Transfer, Hole Transfer
