unfix, bin and minimization

Dear Dr. Steve and others,

Can you explain more details about:

1) What is the relevance of the unfix command? If I use several fix commands within one input'script of simulation,
Do we need to put unfix after one fix?

2) From manual I knew the bin value for metals was about 2.0. Actually How to predict the bin's value
for our simulation of the system?

3) If we want to simulate a new system, we may use a minimization command. How many times we need to use this
command in our simulation. Or only one time for the first simulation?

Thank very much for your explanation

Dear Dr. Steve and others,

Can you explain more details about:

1) What is the relevance of the unfix command? If I use several fix commands within one input'script of simulation,
Do we need to put unfix after one fix?

you need the unfix to stop a fix command. e.g. if you want to replace a fix.

2) From manual I knew the bin value for metals was about 2.0. Actually How to predict the bin's value
for our simulation of the system?

the bin value is determined empirically. it controls the tradeoff
between having to
build neighborlists more often and having to many "useless" atoms in them.
for details, see the manual.

3) If we want to simulate a new system, we may use a minimization command. How many times we need to use this
command in our simulation. Or only one time for the first simulation?

this depends entirely on your system. you can use the minimize command
as many times as you want.

axel

Comments below.

Dear Dr. Steve and others,

Can you explain more details about:

1) What is the relevance of the unfix command? If I use several fix commands within one input'script of simulation,
Do we need to put unfix after one fix?

Each fix stays active unless you unfix it. It's that simple.

2) From manual I knew the bin value for metals was about 2.0. Actually How to predict the bin's value
for our simulation of the system?

Do you mean the neighbor list skin? If so, why do you want to "predict" it?
You set it, via the neighbor command.

3) If we want to simulate a new system, we may use a minimization command. How many times we need to use this
command in our simulation. Or only one time for the first simulation?

I don't know. It depends on your initial cofig, whether you need to
minimize before
running dynamics. If you do need to, you shouldn't need to minimize
more than once.