Carbon Nanotube Simulation Descriptions

Ballv02 A non-reactive collision of a buckyball (C60) and an ortho-benzyne molecule (C₆H₄) is observed if benzyne hits C60 after being given an initial velocity of 0.2A/ps. The collision here appears to be elastic.

Ballv05 A reactive collision of C60 and benzyne occurs when the initial velocity of the benzyne is increased from 0.2 to 0.5 A/ps. The resultant product is a monoadduct of benzeyne onto C60. Hoke II et al reported the laboratory preparation (J. Org. Chem. 1992, 57, 5069-5071). It is also supported by our quantum chemistry calculations.

Ballv07 Dissociation of benzyne and C60 is seen when the benzyne is given a very high initial velocity of 1.5 A/ps.

Tube03 A non-reactive collision of a nanotube and benzyne molecule occurs when the benzyne is given an initial velocity of 0.3 A/ps. This is similar to non-reactive collision process previous observed in Ballv02.

Tubev06 A reactive collision of the nanotube and benzyne occurs when the initial velocity of the benzyne molecule hitting the nanotube is increased from 0.3 to 0.6 A/ps. Our quantum chemical calculation showed the feasibility of this reaction but experimental verification has not yet been done.

Tubev065 A reactive collision to bond benzyne onto a nanotube, similar to the previous process in Tubev06, occurs when the velocity and direction of benzyne hitting the nanotube are different (0.65 vs. 0.65A/ps; parallel vs. perpendicular to the tube bond).

NEV 1 The atoms at both ends of the left gear are given an angular velocity, which increases linearly from 0 to 0.2 revolution per ps (rpps) from time 0 to 10 ps, and stays at 0.2 rpps after 10 ps. The powered (left) gear forces the driven (right) gear to rotate. For the first 25 ps, they work well. But heat accumulates. Temperature increases to >1000 K after 25 ps. In this case, input energy could not effectively be converted into rotational energy, and the gears only wiggle. (note: the left gear is always the powered gear in the following MPEGs)

NEV 2 This is a contination of NEV1. If the angular velocity is given a higher value (from 0.2 to 0.4 rpps in this case), the gear can still rotate well even at the higher temperatures. However, the gears stop rotating when temperature increases to 2000 K.

NEV 3 This is a continuation of NEV2. We wanted to see whether or not the gears still work when the input angular velocity is increased further. The answer is no, and the very high temperature generated will eventually melt the nanotube.

NEV 1-3 This is the case of NEV1+NEV2+NEV3 for a 150 ps trajectory (the final 12.5 ps was not included in the MPEG). This simulation shows that nanotube-based molecular gears cannot work well at temperatures higher than 1000K.

Dataset	Rate (rpps)	Time (ps)
NEV 1	.0 - .2	0 - 10
	.2 - .2	10 - 40
NEV 2	.2 - .4	40 - 50
	.4 - .4	50 - 80
NEV 3	.4 - .6	80 - 90
	.6 - .6	90 - 120

NVT 1 We need to keep the temperature constant for the gears to work. The following simulations were done under constant temperature (300K). This animation shows an initial acceleration of gear rotation given by a linear relation: 0 to 0.05 rpps for the initial 10 ps and a constant 0.05 rpps for the following 30 ps.

NVT 2 Rotation rate keeps increasing from 0.05 to 0.07 rpps as input energy to the end atoms of the powered gear is increased. The gears work very well under such conditions.

NVT 3 The gears still work well at the high rotation rate of 0.1 rpps.

NVT 1-3 This is NVT1+NVT2+NVT3 for the full 120 ps trajectory. It shows the rotation process from initial accelaration to final stable rotation (rotation rate from 0 to 0.1 rpps).

NVT 4 Slip 1 Slip occurs if rotation rate > 0.1 rpps. We use higher frame rates to display this slip. It can be seen that slip occurs by tilting the tooth atoms. Fortunately, gear slip does not destroy the teeth. Therefore, the gears will resume functioning if the rotation rate is reduced.

NVT 4 Slip 2 To make sure that reactive slip does not occur, we used Brenner's reactive potential for inter-gear atomic interactions. It turns out that this result is the same as that seen in "NVT 4 slip 1".

NVT 4 Slip 3 Electrostatic interaction has not been taken into account in the previous studies. This simulation considers the effect of placing partial charges on the C and H in the teeth. We did not find a significant difference between these three cases. Perhaps this is because mechanical motion (gear rotation dynamics) is not as sensitive to details of the force field as is local molecular conformational motion. Including those electrostatic interactions gives a more accurate description of benzyne dimer configuration (J. Phy. Chem., 1996 ...), but not interactions of the benzyne teeth.

NVT 3h This one is the same as "NVT 4 Slip 1," except that the frame rate is twice as high. This allows clearer observation of tooth slip.

NVT 5h This shows rotation of gears with longer shafts. The rotation rate is 0.05 rpps. Compared to shorter shaft gears, longer ones need more input energy to start rotating.

NVT Long This one is the same as the NVT5h, except that it is from a longer MD run (100 ps vs. 20 ps).

GEAR 21 Rotation of on-line multiple rows-of-teeth gears (see Fig.6). The gears work well at the initial acceleration stage, but tend to chatter at some speeds.

GEAR 21 slip 1 Like the single rows-of-teeth gears, the on-line multiple rows-of-teeth gears start slipping when the rotation rate is over 0.1 rpps. The slip is still due to tooth tilting. It can be seen that the teeth interface in a T configuration just before slip rather than the parallel face-to-face configuration evident during working conditions.

GEAR 22 This shows rotation of off-line multiple rows-of-teeth gears (see Fig.6). They work better than the on-line multiple rows-of-teeth gears, as expected. Power is delivered to the driven gear more evenly so the T configuration of gear teeth is less pronounced.

GEAR 22 slip 2 If the gear rotation rate is larger that a critical value of 0.1 rpps, the off-line multiple rows-of-teeth gears slip.

Shaft 1 This animation shows that we can power the gear to drive the shaft, converting rotational motion into translational motion (see Fig.7).

Shaft 2 This animation shows that we can convert translation of the shaft into rotation of the gear by powering a shaft to drive a gear.

Small-Large It is expected that it is harder for a small gear to drive a large gear. Interestingly, if the small gear is given a large acceleration, it does not drive the large one at all but instead bounces back and forth several times, like elastic collisions of a small ball between two boards.

Large-Small It should be easier for a large gear to drive a small one. However, their rotation is not always well-controlled since this system requires a more accurate tooth position design than the others do. If the rotation of the large gear is too slow or too fast, this gear system cannot work well.

Large-Small 1 After an initial acceleration period, we operate the gear system at a medium rotation rate.

Large-Small 2 The slip occurs at a certain high rotation rate. Unlike the same-size gears, in this case the large powered gear keeps rotating and the small one stays still while the slip occurs (still due to tooth tilting).

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