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Interfaces with External Software

Overview

NWChem can be interfaced with external software packages by following the instructions below.

The interface can be set either using a pre-exisiting software package or by downloading and compiling the software from the NWChem makefile infrastructure.

Simint integrals library

To generate the Simint library and enable the NWChem interface (only for energy and first derivative code), you need to define the following environment variables at compile time:

  • USE_SIMINT=y (mandatory)
  • SIMINT_MAXAM=“Maximum angular momentum” (optional, default is 3, therefore up to f orbitals)

The following set directives are required in the input file to trigger use of Simint

set int:cando_txs f
set int:cando_nw f

OpenBLAS

To build NWChem with the optimized BLAS and Lapack OpenBLAS library, you need to define the following environment variables at compile time: 

BUILD_OPENBLAS=1
BLAS_SIZE=8

This procedure requires an internet connection to dowload the OpenBLAS source.
Instead, to use a pre-compiled OpenBLAS library, the BLASOPT, LAPACK_LIB and BLAS_SIZE environment variable need to be set.

ScaLAPACK

To build NWChem with the ScaLAPACK library, you need to define the following environment variables at compile time: 

BUILD_SCALAPACK=1
SCALAPACK_SIZE=8

This procedure requires an internet connection to dowload the OpenBLAS source.
Instead, to use a pre-compiled ScaLAPACK library, the SCALAPACK_LIB and SCALAPACK_SIZE environment variable need to be set.

ELPA

To build NWChem with the ELPA eigensolver library, you need first to set the ScaLAPACK settings as described in the previous section and then you need to define the following environment variables at compile time: 

BUILD_ELPA=1

This procedure requires an internet connection to dowload the OpenBLAS source.
Instead, to use a pre-compiled ELPA library, the ELPA and ELPA_SIZE environment variable need to be set.

Plumed

The BUILD_PLUMED environment variable installs Plumed and interfaces it with the qmd module. This procedure requires an internet connection to dowload the Plumed source.

Instead, if you wish to use an existing Plumed installation, the following environment variables must be set (after having unset BUILD_PLUMED): 

USE_PLUMED=1

Requirements: * The environment variable PATH should to point to the location of the plumed command and LD_LIBRARY_PATH should point to the location of the plumed libraries. * BLAS_SIZE and SCALAPACK_SIZE must be equal to 4 (this is not a requirement when using BUILD_PLUMED)

Libxc

Building NWChem with the libxc DFT library requires setting the environment variable USE_LIBXC=1.

This procedure requires an internet connection to dowload the Libxc source.

Instead, if you wish to use an existing libxc library, the following environment variables must be set, after having unset USE_LIBXC:

  • LIBXC_INCLUDE location of the libxc C header files
  • LIBXC_MODDIR location of the libxc fortran90 module files
  • LIBXC_LIB location of the libxc libraries files

For example, for Debian/Ubuntu systems, the following is needed after having installed the libxc-dev package

    unset USE_LIBXC
    export LIBXC_LIB=/usr/lib/x86_64-linux-gnu
    export LIBXC_INCLUDE=/usr/include

For example, for Fedora systems, the following is needed after having installed the libxc-devel package

    unset USE_LIBXC
    export LIBXC_LIB=/usr/lib64
    export LIBXC_INCLUDE=/usr/include 
    export LIBXC_MODDIR=/usr/lib64/gfortran/modules

XTB

Building NWChem with the Light-weight tight-binding framework tblite requires

  • setting the environment variable USE_TBLITE=1
  • adding xtb to list of NWCHEM_MODULES

Example:

make nwchem_config NWCHEM_MODULES='tinyqmpw xtb'
export USE_TBLITE=1
make