Subject: Re: Simulation of metals

From: Howard Alper <[email-masked]>
Date: Mon, 04 May 1998 11:51:21 -0500

Hello all,

  Some time back I asked the list for information on the simulation of
metals using CHARMM or DISCOVER.  Below is a summary of the responses.
I apologize for the delay.  A belated thanks to all who answered my
query.

  Sincerely,

  Howard Alper

_____________________________________________________________________

Dear Dr. Alper
I have done and seen several papers on metal surface simulations (most
of the metals).I used the De Pristo's CEM potential.  I have seen people 
using EAM.  I guess the codes are available from the authors free of
cost for academic use.  They have their own MD codes, so I am afraid 
they cannot be easily integrated with CHARMM or DISCOVER. But, De
Pristo's code is pretty easy to follow and can be modied very easily.

Sincerely

Vijaya Kumar

_____________________________________________________________________

Dear Dr. Alper
I dont have de Pristo's email address but I know he is with Iowa State
University's Chemistry department.  You can contact Prof. Barbara
Garrison at P ennState Univ. She also used his code and her email
address is [email-masked] You can just do a literature search
on De Pristo or Garrison.  There will bemany actually tons of
papers on metal simulations.  I have just published one paper on such
stuff in JCP in 1997.  I used CEM potential to simulate Cu 100 surface.
I used smart MCrather than MD.  For my own entertainment, I did
simulation Ag, Au and Ni surfaces with MD.  They dont take really that
long.  For about 100ps it is typically less than a day on RS6000 kind of
machine.   I am mainly a solvation dynamics guy worked most of my career
with liquid simulations. Of course, I am familiar with the work
that you publised with Ron Levy.  Where are you located now?  I thought
you  were working for some industry earlier at Boston.

With warm regards
Vijaya Kumar

_____________________________________________________________________

There is plenty of simulations on bulk metals and precisely due to
reason you've mentioned, doing it with DISACOVER or CHARMM is not a good
idea IMHO. Metals usually have multi-bodu interactions and not very 
long-range interactions. I would try to write the MD code from the
scratch. OIt's not that difficult you can actually start with examples
from let's say Allen & Tildesley or othe rsimulations textbook and use
codes given thereas a starting point, all you would have to do is
basically write your own force routine. As the interactions are not
lon-ranged, using of neighbor lists or linked-cells will be very
helpful.

Hope this helps,
Mike

Michael J. Kotelyanskii 
_____________________________________________________________________

Hello, howard

Please check the page of : 

Theoretical Division and Center For Nonlinear Studies,
L.A.N.L., They did the massivley para. MD of metal crack.

Dayong He
_____________________________________________________________________

Dear Howard,

  My post-doc and I are studying Cu and Al (bulk, and with defects
such as vacancies, surfaces, and grain boundaries) using two home-grown
codes:  VERNET (planewave pseudopotential electronic structure code)
and pdQ (MD simulation).  Both are oriented toward periodic (i.e. bulk)
systems.  VERNET is a parallel code, pdQ is in the process of being
parallelized.  We are also trying to develop improved (beyond EAM) force
fields for these materials by 'normalizing' to the static electronic
structure results.  At present, pdQ is in too-primitive shape to release
outside our group, but if you are interested in obtaining the code when
it is ready for prime-time, I can add your name to the request list.
(VERNET is currently being distributed under a beta-test agreement to
interested
parties).

  Regards,

  - Susan Atlas

_____________________________________________________________________
I would recommend taking a look at Effective Medium Theory,
which is a technique well suited for (essentially designed for) 
MD calculations on metals.  A fairly nice, easy to use, implementation
is available from: http://www.fysik.dtu.dk/~stoltze/artwork/artwork.html

I hope this helps.

-greg landrum

_____________________________________________________________________

There has beed a reasonable amount of work on MD simulation of metals,
which you will find in the solid-state physics literature.  As you
rightly say the forces in metals are not simply pairwise decomposable,
and the main approaches are those of having a volume-dependent term,
or of the embedded-atom or Finnis-Sinclair potentials.  If you do a
literature search for the works of Mike W. Finnis or check out his
web site at Queens Uni, Belfast (probably www.qub.ac.uk) you will
likely find some pointers.

The potential-based approaches have had some modest success for
nearly-free electron metals such as the alkali metals, but complex
transition metals with all the effects of complex fermi surfaces
strongly correlated electrons are a different kettle of fish.  The
intertwining of electronic and crystal structural properties
characteristic of metals is one of the main reasons that most serious
work in the field now uses ab-inito methods.  

I advise you to think carefully about what you hope to get out of the
simulations and whether the models are up to delivering it. It's easy
to come from the chemical/molecules world and imagine that pair and
other potentials can be tweaked to give you an accurate model.  In the
world of solids that isn't necessarily so. Metals are much harder to
model, and the Transition metals the most difficult of all.

If you do go ahead with something like a Finnis-Sinclair potential,
there may be some MD codes out there which handle embedded-atom style
potentials, but you will almost certainly have to do some coding
yourself.

sincerely

Keith Refson
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My colleague Bob (R.A.) Johnson has spent his career working in metal
simulations.  I am in Ohio at the momnet but I can send you some
references when I get home to VA.  He uses the three and four body
interactions in his own codes which are not any more difficult or time
consuming than the molecular mechanics.  I suggest you look into those
types of calculations if you want beleivable results.

Barry Farmer
____________________________________________________________________

-- 

Howard E. Alper, Ph.D.
Dept. of Chemistry and The Advanced Materials Research Institute
University of New Orleans
New Orleans, LA 70148
504-280-7216

 - Helping molecules find happiness for almost a 5th of a century.