doc update

docs/src/index.md

@@ -12,6 +12,61 @@ The documentation for TeNLib can be found [**here**](https://titaschanda.github.
 
 ## Overview
 
-Currently, TeNLib contains codes for
+TeNLib features popular Tensor Network (TN) codes with multi-layered abstraction, that provides varyling level of control to the user. Currently, TeNLib contains codes for
 * *(a)* Finite-size Matrix-Product States (MPS): Different varaints of DMRG and TDVP (including subspace expansion).
-* *(b)* Tree Tensor Network (TTN): Variational search for the ground state and first few excited states.
+* *(b)* Tree Tensor Network (TTN): Variational search for the ground state and first few excited states.
+
+
+## Installation
+
+Currently, TeNLib.jl is not registered on Julia General Registry. To install the library (along with ITensors.jl), you can use the following steps:
+
+```
+$ julia
+
+julia> ]
+
+pkg> add ITensors
+
+pkg> add https://github.com/titaschanda/TeNLib.jl
+```
+
+## Future functionality?
+
+Here is a list for future additions in the decreasing order of priority. Any help / suggestions will be helpful.
+* Augmented Tree Tensor Network (aTTN) for variational ground state search for 2D problems.
+* Infinite DMRG (iDMRG) and/or Variational Uniform Matrix Product States (VUMPS) to tackle 1D / quasi-1D problems directly at the thermodynamic limit.
+* Projected Entangled Pair States (PEPS) for 2D problems.
+* Real-time evolution method using PEPS and TTN.
+
+## Example: A simple DMRG code
+
+The following code is for a simple DMRG run at the highest level of abstraction without any additional control.
+
+```
+using ITensors
+using TeNLib
+
+let
+    N = 32
+    sites = siteinds("S=1/2",N; conserve_qns = qn)
+    os = OpStrings()
+    
+    for j=1:N-1
+        os += 1, "Sz" => j,"Sz" => j+1
+        os += 0.5, "S+" =>j, "S-" => j+1
+        os += 0.5, "S-"=>j, "S+" => j+1
+    end
+    
+    H = CouplingModel(os,sites)
+    states = [isodd(n) ? "Up" : "Dn" for n in 1:N]
+    psi0 = MPS(sites, states)
+
+    params = DMRGParams(;nsweeps = [5, 5], maxdim = [20, 50],
+                        cutoff = 1e-14, noise = 1e-3, noisedecay = 2,
+                        disable_noise_after = 3)
+
+    # dmrg2 for two-site DMRG
+    en, psi = dmrg2(psi0, H, params)
+end
+```