- The added line is THIS COLOR.
- The deleted line is THIS COLOR.
This is Eric's logbook for Nano Japan project from 2012.6.3-2012.7.27.
* Daily schedule [#daily]
- 09:00-10:00 Discussion (1)
- 10:00-12:00 Solve the problem and write the progress on pukiwiki
- 12:00-13:30 Lunch
- 13:30-14:30 Discussion (2)
- 14:30-16:30 Solve the problem and write the progress on pukiwiki
- 16:30-17:30 e-mail report and problems
* Goal of the project. [#goal]
- Consider the time evolution of a special vibration (radial breathing mode RBM) of a single wall carbon nanotube after applying the local force at t=0 whose functional shape is a Gaussian in the real space. The time evolution is given by differential equations and solution should be given by animation gif generated by Povray and Giam software. (by R. Saito 2012.5.18)
- Keywords: Coherent phonon, radial breathing mode, carbon nanotubes, Differential equation, Fourier Transform, Povray and Giam, Mathematica
* Assignment for discussion [#discussion]
- Monday: Saito (morning) subject introduction to our lab. Florian (afternoon), differential equations.
- Tuesday: Nugraha (morning + afternoon), subject: concept of coherent phonon.
- Wednesday: Hasdeo (afternoon) subject is missing
- Thursday: Tatsumi (morning) subject: the structure of nanotubes (afternoon) group meeting
- Friday: Tastumi(morning) subject is missing
** Please note: [#notethat]
All appointment should be done by communicating each other on what kind of subjects will you teach.
- If Eric-san asks you what he needs, please answer it with cc to me.
- If you do not have any material to need, please give him an easy question to solve.
- If Eric-san could not answer this question, it means that your question is bad (need some knowledge).
- If Eric-san can answer within 2min, it means that you gave not proper question (answer is trivial).
* What does Eric-san want to [#wishlist]
Please list here with some simple reason or detail.
List from new to old.
Hey guys! So I believe this is where I should post questions. I don't have any specific questions today, but was just trying to understand Brillouin zones and Bloch's theorem, which appear a lot in Saito-sensei's book on Carbon Nanotubes.
From google I have an ok idea of what Brillouin zones are, but am still trying to figure out how they relate to the energy gap of the cell such as on page 28 of the CN book. I was also wondering how on page 47 the Brillouin zone can be a long line segment instead of a polygon.
If anybody has any quick words of advice for how to understand Bloch's theorem that would be great as well! It's a little bit intimidating and I'm not sure if there's a simple way to begin to understand it.
Thanks so much and see you guys in a couple of weeks!
Answer : (Tapsanit) Please consider my answers one by one in order to understand the Brillouin zone.
1. What is the Bloch'theorem written in page. 17 of Saito's book?
A: The electron in solid can behave as wave and its wave function which is
denoted by Psi(r) should satisfy the Bloch's theorem due to the periodicity
of the atoms in solid. The Psi is sometimes called the Bloch wave function.
It can be written as the phase factor exp(ikr) times the periodic function in
real space u(r), u(r+T) = u(r), : Psi(r) = exp(ikr)u(r). It is recommended to
check that the Psi(r)=exp(ikr)u(r) satisfies the Bloch's theorem.
2. What is the Brillouin zone? (not solved)
A: We must understand the reciprocal lattice before answering this question,
because the Brillouin zone is defined from the reciprocal lattice.
3. What is the reciprocal lattice that define the Brillouin zone?
A: As mentioned, the electron in solid is a kind of wave whose wave
function satisfies the Bloch's theorem. This means that it has the
wavevector with amplitude and direction just like normal wave. The dimension
of wavevector is 1/[length] which is a reciprocal of length in real
lattice. Then, reciprocal lattice is constructed to obtain the wavevector
of the electron. Please note that there are many wavevectors possibly
obtained from the reciprocal space. The unit vectors of the reciprocal
lattice (b1,b2,b3) are obtained from the unit vectors of the real lattice
(a1,a2,a3) by following relations
(* denotes dot product of two vectors) :
b1*a1 = 2*Pi, b2*a2 = 2*Pi, b3*a3 = 2*Pi and bi*aj = 0 if i /= j.
It is recommended to try to use this relations to derive the unit vectors of
reciprocal lattice, b1 and b2, of graphene in Eq. (2.23) of Saito's book
using a1 and a2 in Eq. (2.22).
Q2: Copy machine: Can I use the copy machine or printer?
A2: (not solved)
Q1: Library: I would like to know where is the library and how to use it.
A1: (not solved) or (solved) Hasdeo-san brought me to the library directly etc.
* Report [#report]
This part is basically written by Eric-san. Any other people can add this.
Here the information should be from new to old so that we do not need to scroll.
Check that the ?(r)=e^(ik?r) u(r) satisfies the Bloch's theorem:
Bloch?s theorem is: T_a ?=e^(ik?a) ?
T ?_(a ?_i )is a translation operator ? T ?_(a ?_i ) ?(r ?)= ?(r ?+a ?_i)
r ?+(a_i ) ?=r ? because (a_i ) ? is a lattice vector.
u(r) is a periodic function.
T ?_(a ?_i ) ?(r ?)= ?(r ?+a ?_i )=
e^(ik?(r ?+(a_i ) ? ) ) u(r ?+(a_i ) ?)= e^(ik?((a_i ) ? ) ) [e^(ik?(r ? ) ) u(r ?+(a_i ) ?)]=e^(ik?((a_i ) ? ) ) [e^(ik?(r ? ) ) u(r ?)]
Theorem is satisfied.
Derive the unit vectors of reciprocal lattice, b1 and b2, of graphene in Eq. (2.23) of Saito's book using a1 and a2 in Eq. (2.22).
a ?_i=unit vector of real lattice
b ?_i=unit vector or reciprocal lattice
a ?_i?b ?_i=2?
a ?_i?b ?_j=0 if i?j
from eqn 2.22 in CN book:
a ?_1=(?3/2 a,a/2), a ?_2=(?3/2 a,(-a)/2)
a ?_1?b ?_1=a_1x b_1x+a_1y b_1y=b_1x (a?3)/2+b_1y a/2=2?
a ?_2?b ?_1= a_2x b_1x+a_2y b_1y=b_1x (a?3)/2-b_1y a/2=0
?b_1y a/2 = b_1x (a?3)/2
?b_1x (a?3)/2+b_1x (a?3)/2=2?
?b_1x=2?/(a?3) ? ?-b_1y a/2=0 ? b_1y=2?/a
Same process gives: b_2=(2?/(a?3),(-2?)/a)
** June 5 (Hasdeo teaches XX and YY. from 9:00-9:34) etc [#rep20120605]
- Who gave what? (XX min)
- What isr the home work?
- The answer of the home work should be put here.
- Evaluation of the answer by teacher
- Evaluation by Saito
** June 4 [#rep20120604]
- task 1
- task 2
- task 4