Author Topic: molecular dynamics not getting started  (Read 6171 times)

vsharma

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molecular dynamics not getting started
« on: April 26, 2013, 03:08:43 PM »
Hello everyone,

A) I took a coord file (some atoms fixed with 'f') from a previous run and put it in a new folder. I ran 'define' and made a control file, which has def-SV(P) basis set, BP86 functional and RI/MARIJ are on. After this I ran 'mdprep', and I kept everything default. Everything went successful so far. Now when I run this on Turbomole 6.4, the program stops with the error (as shown in job.1 file) :

################

Reading information from mdmaster
Reading log history information from mdmaster
Reading input data from mdlog.1
    WARNING: change in atomic symbol
Checking for non-default isotopic masses in control

No constraints requested.
Reading status from mdmaster
Reading actions from mdmaster

 <getgrd> : data group $grad  is missing

---==>  E R R O R

<getgrad>: coords in $grad differ from those in $current

<getgrad>: coords in $grad differ from those in $current
MOLECULAR DYNAMICS PROBLEM => aimd quits

####################

B) In addition to this, I ran 'mdprep' in another folder which contained all files pertaining to a previously optimized/converged run (specifics were: some atoms fixed, BP86/RI/MARIJ/def2-SVP). 'mdprep' ran successfully after selecting all default values. Now when I made a MD run, the above error was reproduced.

C) Thirdly, I moved the gradient file in this folder (case B) elsewhere and ran 'rdgrad' to generate a new gradient file, and it went fine. And, I can see that the coordinates in gradient file and mdlog.1 file are same, but when I run the MD run, the error mentioned above is again produced.

I am unable to understand that a) when I do not have a gradient file at all (case A), I get the aforementioned error (?) and b) when I have a gradient file (or a newly created one) as in case B and C, the error is still the same.

Could you please briefly mention something about it ? Any help will be much appreciated.

thanks and regards,

Vivek

Arnim

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Re: molecular dynamics not getting started
« Reply #1 on: April 29, 2013, 10:34:58 AM »
Hello Vivek,

the frog program checks, if the last coordinates in the gradient file and in mdlog.x are the same. If a rdgrad step is aborted or something corrupts either of these files, you can encounter this errror message and it makes it hard to continue from there. It is best to start a new trajectory with a clean gradient file at such a point.

Cheers,

Arnim