potential_type for B3LYP, periodic system

[Mozhdeh Mohammadpour]

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. 

[mdsimula...@gmail.com]

Hi,

I am interested in this question as well.

Thanks,

Kenny

[Matt Watkins]

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]

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