[Pw_forum] Structural optimization of Biotin molecule

[Rolly Ng]

Dear QE developers and users,

 

I am trying to run a "relax" structural optimization of the Biotin molecule
on QE-5.2.0, the default nstep=50 does complete but I made a few
observations on the output file.

 

(1) "Check: negative starting charge=   -0.823869" Is this quite large since
I have only 90 electrons? Is it expected to be 0.001*90=0.009 or less
according to the FAQ.
http://www.quantum-espresso.org/faq/self-consistency/#6.12

(2) It ends by the maximum number of steps reached. Is this normal to end
BFGS geometry optimization?

"energy   old            =    -277.9634535886 Ry

  energy   new            =    -277.9645708192 Ry

          CASE: energy  _new < energy  _old

          new trust radius        =       0.1278123491 bohr

          The maximum number of steps has been reached.

          End of BFGS Geometry Optimization"

(3) I have increased the nstep=100 and 1000,  It only takes long to end the
job but still ended by maximum number of steps reached. Which is very
strange.

(4) I have tried to increase  ecutwfc=200.0d0,  ecutrho=800.0d0, then the
negative starting charge becomes much smaller to -0.000171

(5) How can I speed up this task?

 

Please take a look at the input file as attached. Any comment are welcome.

 

Thanks,

Rolly

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