I am using amber12 software used for molecular mechanical force fields for the simulation of biomolecules, I follow the installation instructions described in the next link [Intallation of amber in Mac OS X](http://jswails.wikidot.com/installing-amber12-and-ambertools-12) the program actually works but when in try to execute a program part of the software its stops and says 

> 
> Fortran runtime error: End of file
> 
> 
> 

1.So this is what I do, first access the file folder that contain the files

```
N-terminal-2:~ javieralejandrorendoncarrillo$ cd Desktop/amber/Complex1

```

2.then set the path

```
N-terminal-2:Complex1 javieralejandrorendoncarrillo$ export AMBERHOME=/Users/javieralejandrorendoncarrillo/amber/amber12

```

3.and finally execute the program whit the next command line:

```
N-terminal-2:Complex1 javieralejandrorendoncarrillo$ $AMBERHOME/bin/sander.MPI -O -i min.in -o min_complex.out -p complex.prmtop -c complex.inpcrd -r complex_min.crd &
[2] 13377
N-terminal-2:Complex1 javieralejandrorendoncarrillo$ At line 524 of file mdread.F90 (unit = 5, file = 'min.in')
Fortran runtime error: End of file

[2]-  Exit 2                  $AMBERHOME/bin/sander.MPI -O -i min.in -o min_complex.out -p complex.prmtop -c complex.inpcrd -r complex_min.crd
N-terminal-2:Complex1 javieralejandrorendoncarrillo$ 

```

The file `min.in` is saved in file folder `Complex 1` where I'm running the simulation this is the script for `min.in`

```
Initial minimisation of our complex
 &cntrl
  imin=1, maxcyc=3000, ncyc=2500,
  cut=16, ntb=0, igb=1,
 &end

```

How do I solve this problem? Is the syntax wrong? Does anyone know how to execute or what kind of programming language is this?

This is the version installed of gfortran I have

```
N-terminal-2:~ javieralejandrorendoncarrillo$ gfortran -v
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/opt/local/libexec/gcc/x86_64-apple-darwin12/4.7.2/lto-wrapper
Target: x86_64-apple-darwin12
Configured with: ../gcc-4.7.2/configure --prefix=/opt/local --build=x86_64-apple-darwin12 --enable-languages=c,c++,objc,obj-c++,lto,fortran,java --libdir=/opt/local/lib/gcc47 --includedir=/opt/local/include/gcc47 --infodir=/opt/local/share/info --mandir=/opt/local/share/man --datarootdir=/opt/local/share/gcc-4.7 --with-libiconv-prefix=/opt/local --with-local-prefix=/opt/local --with-system-zlib --disable-nls --program-suffix=-mp-4.7 --with-gxx-include-dir=/opt/local/include/gcc47/c++/ --with-gmp=/opt/local --with-mpfr=/opt/local --with-mpc=/opt/local --with-ppl=/opt/local --with-cloog=/opt/local --enable-cloog-backend=isl --disable-cloog-version-check --enable-stage1-checking --disable-multilib --enable-lto --enable-libstdcxx-time --with-as=/opt/local/bin/as --with-ld=/opt/local/bin/ld --with-ar=/opt/local/bin/ar --with-bugurl=https://trac.macports.org/newticket --disable-ppl-version-check --with-pkgversion='MacPorts gcc47 4.7.2_2'
Thread model: posix
gcc version 4.7.2 (MacPorts gcc47 4.7.2_2) 

```