potential_type for B3LYP, periodic system

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Mozhdeh Mohammadpour

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Oct 11, 2021, 7:16:40 AM10/11/21
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Hi, 

I am trying to optimize alpha glycine with B3LYP. It is supposed to use the TRUNCATED or SHORTRANGE type of potential in the HF section. 
1) I would like to know that which one is is a better choice?
Alpha glycine has a monoclinic unit cell. 

   &CELL
      ABC  4.9669 11.459 5.4231
      ALPHA_BETA_GAMMA 90.0 114.916 90.0
      SYMMETRY MONOCLINIC
   &END CELL

2) Should I use the smallest unit cell parameter for choosing CUTOFF_RADIUS?
P.S. Please find my attached input. 
a-Gly.inp

mdsimula...@gmail.com

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Nov 4, 2021, 12:12:59 PM11/4/21
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Hi,

I am interested in this question as well.

Thanks,
Kenny

Matt Watkins

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Nov 5, 2021, 10:14:44 AM11/5/21
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Hello.
You should use a truncated interaction potential. The short-range potential is normally for the split (erf + erfc) models like HSE.
Yes, the maximum safe truncation radius will be approximately half the smallest box length - you'll need at least a 10 angstrom box for quantitative work.
Matt

Mozhdeh Mohammadpour

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Nov 22, 2021, 8:17:57 AM11/22/21
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Hi Matt,

Thanks for your helpful response. 
Yes, I used ' MULTIPLE_UNIT_CELL 3 3 3' to enlarge the box and a  CUTOFF_RADIUS  of 6. 

Mozhdeh
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