From cc5565b7176980ca0d63720b580a407808077bf7 Mon Sep 17 00:00:00 2001
From: Anton Akhmerov <anton.akhmerov@gmail.com>
Date: Wed, 21 Dec 2016 18:11:22 +0100
Subject: [PATCH] automatically extend period of attached leads
---
kwant/builder.py | 22 ++++++++++++++++------
kwant/tests/test_builder.py | 13 +++++++++++++
2 files changed, 29 insertions(+), 6 deletions(-)
diff --git a/kwant/builder.py b/kwant/builder.py
index 90c22623..b3eaf2b4 100644
--- a/kwant/builder.py
+++ b/kwant/builder.py
@@ -1270,12 +1270,22 @@ class Builder:
if sym.num_directions != 1:
raise ValueError('Only builders with a 1D symmetry are allowed.')
- for hopping in lead_builder.hoppings():
- if not -1 <= sym.which(hopping[1])[0] <= 1:
- msg = ('The following hopping connects non-neighboring lead '
- 'unit cells. Only nearest-cell hoppings are allowed '
- '(consider increasing the lead period).\n{0}')
- raise ValueError(msg.format(hopping))
+
+ try:
+ hop_range = max(abs(sym.which(hopping[1])[0])
+ for hopping in lead_builder.hoppings())
+ except ValueError: # if there are no hoppings max() will raise
+ hop_range = 0
+
+ if hop_range > 1:
+ # Automatically increase the period, potentially warn the user.
+ new_lead = Builder(sym.subgroup((hop_range,)))
+ new_lead.fill(lead_builder, next(iter(lead_builder.sites())),
+ max_sites=float('inf'))
+ lead_builder = new_lead
+ sym = lead_builder.symmetry
+ H = lead_builder.H
+
if not H:
raise ValueError('Lead to be attached contains no sites.')
diff --git a/kwant/tests/test_builder.py b/kwant/tests/test_builder.py
index 2f497277..6d9573b2 100644
--- a/kwant/tests/test_builder.py
+++ b/kwant/tests/test_builder.py
@@ -755,6 +755,19 @@ def test_attach_lead():
assert len(list(syst.sites())) == 6
syst.attach_lead(lead, fam(-5))
assert set(syst.leads[0].interface) == set([fam(-1), fam(0)])
+
+ # add some further-than-nearest-neighbor hoppings
+ hop_range = 3
+ lead = builder.Builder(VerySimpleSymmetry(1))
+ lead[fam(0)] = 1
+ for i in range(1, hop_range + 1):
+ lead[fam(0), fam(i)] = 1
+ syst.attach_lead(lead)
+ expanded_lead = syst.leads[-1].builder
+ assert expanded_lead.symmetry.period == hop_range
+ assert len(list(expanded_lead.sites())) == hop_range
+
+ # check that we can actually finalize the system
syst.finalized()
--
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