DEHam/README.md

# DEHam

Double Exchange Hamiltonian: Complete Version
=============================================

1. Dependencies
---------------

  1. [PETSc](https://www.mcs.anl.gov/petsc/documentation/installation.html) and [SLEPc](http://slepc.upv.es/documentation/current/docs/instal.htm)

  2. [IRPF90](https://github.com/scemama/irpf90)

2. Compiling
------------

  1. Export environment variables for PETSc and SLEPc

	```shell
	export PETSC_DIR=${PATH_TO_PETSC_INSTALLATION}
	export SLEPC_DIR=${PATH_TO_SLEPC_INSTALLATION}
	```

  2. Make the executable

	```shell
	make ex1
	```

3. Using DEHam
---------------

  1. The DEHam program requires an input file which 
   has the topology of the Hamiltonian and the various parameters
   as explained below in a sample inputfile:

	```python
	140					# The total number of determinants
	7					# The largest number of non-zero elements per row
	2					# The number of processors used in parallel
	1					# The number of holes
	0					# The isz (ms-1/2) value
	1,2,3,1,2,3,4,5,6,7	# The topology of the system is specified here
	2,3,4,8,7,6,5,6,7,8	# first and second line contain the two sites linked
	1,1,1,2,2,2,2,3,3,3	# third line contains the type of link (1 for t, J 2 for K and 3 for none)
	.1430,-0.20,0.0000	# The three types of links this line gives J, K
	.1430,-0.20,0.0000	# 
	-1.00,0.0,0.00		# This line gives t
	```

  2. running DEHam

	```shell
	mpiexec -n [nprocs] ./ex1 inpfile 
	```