Re: [Sci.nanotech] Error in Allis and Drexler paper

[ Moderator's note: The following is a cleaned-up version of a post from
Perry from a couple days ago. Somewhere along the way it got mangled
to an almost unreadable state. My apologies for not addressing this on
the original approval - the response from Drexler is precisely what the
original poster was looking for and I appreciate Perry's contacting
Drexler for a response. -JimL ]

Toby Kelsey <toby_kelsey@xxxxxxxxxxxx> writes:
I have just read "Design and Analysis of a Molecular Tool for Carbon
Transfer in Mechanosynthesis" by Allis and Drexler
(J. Comput. Theor. Nanosci. 2, 4555, 2005), available online at
<http://e-drexler.com/d/05/00/DC10C-mechanosynthesis.pdf>, and it
seem to me that there is a basic error in their calculations. In
section 4.4 they compute the probability[...]

I asked Eric Drexler for comment. He wrote me this (I think he did not
understand who had made the original comment):

From: K.Eric Drexler
Subject: Re: Error in Allis and Drexler paper
To: "Perry E. Metzger"
Cc: Damian Gregory Allis
Date: Tue, 31 Jan 2006 11:03:23 -0800

Dear Perry,

Thank you for reading and examining "Design and Analysis of a
Molecular Tool for Carbon Transfer in Mechanosynthesis". If I am
not mistaken, the model of configurational entropy effects
suggested by your note would, if taken literally, indicate an
error rate of 100% for all placement operations. Also, any error
rate that operated on a "per vibration" basis would approach 100%
in the limit of slow placement motions. These results cannot be
right.

Regarding more realistic estimates of placement errors, please
examine Section 6.3, "Placement Errors" (pp 130 - 134) of
Nanosystems, which addresses this issue. The approximations
presented there of course take account of configurational entropy;
as you suggest, omitting this would be a very elementary mistake.

Would you please post this note where it will be seen by readers
of your original comment?

With best wishes,

-- Eric

.