Posted by Victor on September 08, 2014 at 13:04:15:

In Reply to: Re: THRESHOLD in SEWARD posted by Jesus Gonzalez Vazquez on September 04, 2014 at 16:53:38:

Hi Jesus,

the 'THRESHOLD' is relevant only without packing of two-electron integrals (ERIs). By default, packing of ERIs is activated. So, if you want to discard integrals, you should specify an additional option - "NoPack". However, that is very brutal and extremely inaccurate way for packing ERIs and reducing the disk storage demands. I suggest you to consider using the Cholesky Decomposition method. The CD method is consistent and robust/accurate packing scheme. Please check the following SEWARD's option:

"Cholesky","THRCholesky", "Low Cholesky", "Medium Cholesky", "High Cholesky"

With best regards,

Victor.

: Hi,

: Thank you very much for your answer, I checked it with a diatomic molecule (but a big basis set). The input:

: &SEWARD

: Basis set

: H.aug-cc-pV5Z...

: H -1. 0. 0.

: End of Basis

: Basis set

: Cl.aug-cc-pV5Z...

: Cl +1. 0. 0.

: End of Basis

: THRESHOLD=...

: End of Input

: In case of 1e-14 (default), the output is saving:

: Integrals are written in MOLCAS2 format

: Number of integrals written on Disk = 500237956

: Number of nonzero integrals = 134879021

: Packing accuracy = 0.1000E-13

: Highest disk address written 2230852

: Diagonal and subdiagonal, symmetry allowed 2-el integral blocks are stored on Disk

: The size of the OrdInt: 1115432KB

: If one uses 100:

: Integrals are written in MOLCAS2 format

: Number of integrals written on Disk = 500237956

: Number of nonzero integrals = 0

: Packing accuracy = 0.1000E-13

: Highest disk address written 1955396

: Diagonal and subdiagonal, symmetry allowed 2-el integral blocks are stored on Disk

: The size of OrdInt: 977704KB

: There is a very tiny reduction of the file... so I cannot understand how it works, how big are the blocks?

: Thank you again,

: Jesus

: : Hi,

: : this is a poor example since it is atomic. The integrals are written to the disk in blocks. In this atomic case the number of integrals does not exceed a singel block and reducing the number of nonzero integrals will not reduce the number of blocks in the disk. Try a larger molecular system to see the effect.