## Monday, June 22, 2009

### molecular gear published in Nature Materials

Step-by-step rotation of a molecule-gear mounted on an atomic-scale axis

C. Manzano1*,W.-H. Soe1*, H. S.Wong, F. Ample, A. Gourdon, N. Chandrasekhar and C. Joachim1,2

compared to the small bearing (disassembled) of old:

## Saturday, June 13, 2009

## Monday, June 1, 2009

### MATLAB function to calculate the energy of double wall carbon nanotubes

function [U dr dt]=DWNT(n1, m1, n2, m2)

% this function uses the chiral vectors of two carbon nanotubes as inputs

%(n1 m1)-inner & (n2 m2)-outer and returns the energy of the tube in kcal

%mol^-1 atom^-1 using an empirical equation found in

%"Double-Wall carbon nanotubes...",

%Bakalis & Zerbetto, Chemical Physics Letters 463 (2008) 139-140

%function written by Tom Moore

%define energy constants

a= 1665.51; %kcal A^6 mol^-1 atom^-1

b= -92.85; %kcal A^3 mol^-1 atom^-1

c= 2.50; %kcal A^1 mol^-1 atom^-1

d= 17.24 ; %kcal A^4 mol^-1 atom^-1

f= -58.56; %kcal A^5 mol^-1 atom^-1

%define graphene lattice constant in A

k= 2.49;

% calculate the chiral angles of both tubes in radians

t1_rad=acos((2*n1+m1)/(2*(n1^2+m1^2+n1*m1)^.5));

t2_rad=acos((2*n2+m2)/(2*(n2^2+m2^2+n2*m2)^.5));

dt=t1_rad-t2_rad %may need to do a <1 check here

% calculate the radius of both tubes

r1=(2.49*(n1^2+m1^2+n1*m1)^.5)/(2*pi);

r2=(2.49*(n2^2+m2^2+n2*m2)^.5)/(2*pi);

dr= r2-r1;

%find the energy of the tube

A= (a/dr^6)+(b/dr^3)+(c/dr);

B=sin(dt)*cos(dt);

C=(d/dr^4)+(f/dr^5);

U=A+B*C

% this function uses the chiral vectors of two carbon nanotubes as inputs

%(n1 m1)-inner & (n2 m2)-outer and returns the energy of the tube in kcal

%mol^-1 atom^-1 using an empirical equation found in

%"Double-Wall carbon nanotubes...",

%Bakalis & Zerbetto, Chemical Physics Letters 463 (2008) 139-140

%function written by Tom Moore

%define energy constants

a= 1665.51; %kcal A^6 mol^-1 atom^-1

b= -92.85; %kcal A^3 mol^-1 atom^-1

c= 2.50; %kcal A^1 mol^-1 atom^-1

d= 17.24 ; %kcal A^4 mol^-1 atom^-1

f= -58.56; %kcal A^5 mol^-1 atom^-1

%define graphene lattice constant in A

k= 2.49;

% calculate the chiral angles of both tubes in radians

t1_rad=acos((2*n1+m1)/(2*(n1^2+m1^2+n1*m1)^.5));

t2_rad=acos((2*n2+m2)/(2*(n2^2+m2^2+n2*m2)^.5));

dt=t1_rad-t2_rad %may need to do a <1 check here

% calculate the radius of both tubes

r1=(2.49*(n1^2+m1^2+n1*m1)^.5)/(2*pi);

r2=(2.49*(n2^2+m2^2+n2*m2)^.5)/(2*pi);

dr= r2-r1;

%find the energy of the tube

A= (a/dr^6)+(b/dr^3)+(c/dr);

B=sin(dt)*cos(dt);

C=(d/dr^4)+(f/dr^5);

U=A+B*C

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