TeraChem interface

TeraChem is a quantum chemistry code written exclusively for the Nvidia GPU. The program is commercial, however, the demo version can be used for up to 15 minutes per session.

ASH features a simple interface to it that allows TeraChem energy+gradient calculations on the GPU. Can be used in a QM/MM setting allowing both the QM and MM steps to run on the GPU via TeraChem and OpenMM. Interface is a bit limited at the moment.

TeraChemTheory class:

class TeraChemTheory:
    def __init__(self, terachemdir=None, filename='terachem', printlevel=2,
                teracheminput=None, numcores=1):

Keyword	Type	Default value	Details
terachemdir	string	None	Directory where TeraChem binaries are.
teracheminput	Python dict	None	Python dictionary containing string key-value pairs of TeraChem input options.
printlevel	integer	2	Printlevel
filename	string	'terachem'	Filename used for TeraChem input/output files.

TeraChem needs to be installed separately.

DFT-SCF example:

from ash import *
frag = Fragment(databasefile="h2o.xyz", charge=0, mult=1)

#Python dictionary with TeraChem input options. See manual: http://www.petachem.com/doc/userguide.pdf
teracheminput_dict={
'method':'ublyp',
'basis':'6-31g*',
'sphericalbasis':'false',
'scf':'diis+a',
'timings':'yes'
}

terachem = TeraChemTheory(teracheminput=teracheminput_dict)

Singlepoint(theory=terachem, fragment=frag)

GPU control:

How Terachem runs on the GPU/GPUs is controlled outside of ASH via environment variables. The most important variable to control is what GPU device to use (1 or multiple).

#Use GPU device 0 and 1
export CUDA_VISIBLE_DEVICES=0,1