#!/bin/sh

# run from directory where this script is
cd `echo $0 | sed 's/\(.*\)\/.*/\1/'` # extract pathname
EXAMPLE_DIR=`pwd`

# check whether echo has the -e option
if test "`echo -e`" = "-e" ; then ECHO=echo ; else ECHO="echo -e" ; fi

$ECHO
$ECHO "$EXAMPLE_DIR : starting"
$ECHO
$ECHO "This example shows how to use pw.x to perform electronic structure"
$ECHO "calculations in the presence of a finite homogeneous electric field "
$ECHO "described through the modern theory of the polarization. The example"
$ECHO "shows how to calculate high-frequency dielectric constant of bulk Silicon"

# set the needed environment variables
. ../../../environment_variables

# required executables and pseudopotentials
BIN_LIST="pw.x"
PSEUDO_LIST="Si.pbe-rrkj.UPF"

$ECHO
$ECHO "  executables directory: $BIN_DIR"
$ECHO "  pseudo directory:      $PSEUDO_DIR"
$ECHO "  temporary directory:   $TMP_DIR"
$ECHO "  checking that needed directories and files exist...\c"

# check for directories
for DIR in "$BIN_DIR" "$PSEUDO_DIR" ; do
    if test ! -d $DIR ; then
        $ECHO
        $ECHO "ERROR: $DIR not existent or not a directory"
        $ECHO "Aborting"
        exit 1
    fi
done
for DIR in "$TMP_DIR" "$EXAMPLE_DIR/results" ; do
    if test ! -d $DIR ; then
        mkdir $DIR
    fi
done
cd $EXAMPLE_DIR/results

# check for executables
for FILE in $BIN_LIST ; do
    if test ! -x $BIN_DIR/$FILE ; then
        $ECHO
        $ECHO "ERROR: $BIN_DIR/$FILE not existent or not executable"
        $ECHO "Aborting"
        exit 1
    fi
done

# check for pseudopotentials
for FILE in $PSEUDO_LIST ; do
    if test ! -r $PSEUDO_DIR/$FILE ; then
       $ECHO
       $ECHO "Downloading $FILE to $PSEUDO_DIR...\c"
            $WGET $PSEUDO_DIR/$FILE $NETWORK_PSEUDO/$FILE 2> /dev/null
    fi
    if test $? != 0; then
        $ECHO
        $ECHO "ERROR: $PSEUDO_DIR/$FILE not existent or not readable"
        $ECHO "Aborting"
        exit 1
    fi
done
$ECHO " done"


# how to run executables
PW_COMMAND="$PARA_PREFIX $BIN_DIR/pw.x $PARA_POSTFIX"
$ECHO
$ECHO "  running pw.x as: $PW_COMMAND"
$ECHO

cat > si.scf.efield.in << EOF
&control
    calculation='scf'
    restart_mode='from_scratch',
    prefix='silicon',
    lelfield=.true.,
    nberrycyc=1
    pseudo_dir='$PSEUDO_DIR/',
    outdir='$TMP_DIR/'

 /
 &system
    ibrav= 1, celldm(1)=10.18, nat=  8, ntyp= 1,
    ecutwfc = 20.0
 /
 &electrons
    diagonalization='david',
    conv_thr =  1.0d-8,
    mixing_beta = 0.5,
    startingwfc='random',
    efield_cart(1)=0.d0,efield_cart(2)=0.d0,efield_cart(3)=0.d0
 /
ATOMIC_SPECIES
 Si  28.086 Si.pbe-rrkj.UPF
ATOMIC_POSITIONS
 Si -0.125 -0.125 -0.125
 Si  0.375  0.375 -0.125
 Si  0.375 -0.125  0.375
 Si -0.125  0.375  0.375
 Si  0.125  0.125  0.125
 Si  0.625  0.625  0.125
 Si  0.625  0.125  0.625
 Si  0.125  0.625  0.625
K_POINTS {automatic}
3 3 7 0 0 0
EOF
$ECHO "  running the PW calculation for bulk Si E_field=0.0  a.u. ...\c"
$PW_COMMAND < si.scf.efield.in > si.scf.efield.out
check_failure $?
$ECHO " done"

cat > si.scf.efield2.in << EOF
 &control
    calculation='scf'
    restart_mode='from_scratch',
    prefix='silicon',
    lelfield=.true.,
    nberrycyc=3
    pseudo_dir='$PSEUDO_DIR/',
    outdir='$TMP_DIR/'

 /
 &system
    ibrav= 1, celldm(1)=10.18, nat=  8, ntyp= 1,
    ecutwfc = 20.0
 /
 &electrons
    diagonalization='david',
    conv_thr =  1.0d-8,
    mixing_beta = 0.5,
    startingwfc='random',
    efield_cart(1)=0.d0,efield_cart(2)=0.d0,efield_cart(3)=0.001d0
 /
ATOMIC_SPECIES
 Si  28.086 Si.pbe-rrkj.UPF
ATOMIC_POSITIONS
 Si -0.125 -0.125 -0.125
 Si  0.375  0.375 -0.125
 Si  0.375 -0.125  0.375
 Si -0.125  0.375  0.375
 Si  0.125  0.125  0.125
 Si  0.625  0.625  0.125
 Si  0.625  0.125  0.625
 Si  0.125  0.625  0.625
K_POINTS {automatic}
3 3 7 0 0 0
EOF
$ECHO "  running the PW calculation for bulk Si E_field=0.001  a.u. ...\c"
$PW_COMMAND < si.scf.efield2.in > si.scf.efield2.out
check_failure $?
$ECHO " done"

# clean TMP_DIR
$ECHO "  cleaning $TMP_DIR...\c"
rm -rf $TMP_DIR/silicon*
$ECHO " done"

$ECHO
$ECHO "$EXAMPLE_DIR : done"