From b9f43ec416709d57366027cdde34668124a535ad Mon Sep 17 00:00:00 2001
From: Anton Akhmerov <anton.akhmerov@gmail.com>
Date: Mon, 18 Feb 2013 18:15:12 -0500
Subject: [PATCH] fix bug in TranslationalSymmetry.reversed
---
kwant/lattice.py | 26 ++++++++++++--------------
1 file changed, 12 insertions(+), 14 deletions(-)
diff --git a/kwant/lattice.py b/kwant/lattice.py
index 4b1b67d3..c0069ad1 100644
--- a/kwant/lattice.py
+++ b/kwant/lattice.py
@@ -245,6 +245,7 @@ class TranslationalSymmetry(builder.Symmetry):
# A dictionary containing cached data required for applying the
# symmetry to different site groups.
self.site_group_data = {}
+ self.is_reversed = False
def add_site_group(self, gr, other_vectors=None):
"""
@@ -326,7 +327,8 @@ class TranslationalSymmetry(builder.Symmetry):
def which(self, site):
det_x_inv_m_part, det_m = self._get_site_group_data(site.group)[-2:]
- return ta.dot(det_x_inv_m_part, site.tag) // det_m
+ result = ta.dot(det_x_inv_m_part, site.tag) // det_m
+ return -result if self.is_reversed else result
def act(self, element, a, b=None):
m_part = self._get_site_group_data(a.group)[0]
@@ -335,6 +337,8 @@ class TranslationalSymmetry(builder.Symmetry):
except ValueError:
msg = 'Expecting a {0}-tuple group element, but got `{1}` instead.'
raise ValueError(msg.format(self.num_directions, element))
+ if self.is_reversed:
+ delta *= -1
if b is None:
return builder.Site(a.group, a.tag + delta, True)
elif b.group is a.group:
@@ -348,6 +352,8 @@ class TranslationalSymmetry(builder.Symmetry):
msg = 'Expecting a {0}-tuple group element, ' + \
'but got `{1}` instead.'
raise ValueError(msg.format(self.num_directions, element))
+ if self.is_reversed:
+ delta2 *= -1
return builder.Site(a.group, a.tag + delta, True), \
builder.Site(b.group, b.tag + delta2, True)
@@ -357,20 +363,12 @@ class TranslationalSymmetry(builder.Symmetry):
def reversed(self):
"""Return a reversed copy of the symmetry.
- The result is identical to creating a new symmetry with all the
- period vectors opposite to the original but with the same fundamental
- domain.
+ The resulting symmetry has all the period vectors opposite to the
+ original and an identical fundamental domain.
"""
- periods = [[-i for i in j] for j in self.periods]
- result = TranslationalSymmetry(*periods)
- for gr in self.site_group_data:
- m_part, det_x_inv_m_part, det_m = self.site_group_data[gr]
- if self.num_directions % 2:
- det_m = -det_m
- else:
- det_x_inv_m_part = -det_x_inv_m_part
- m_part = -m_part
- result.site_group_data[gr] = (m_part, det_x_inv_m_part, det_m)
+ result = TranslationalSymmetry(*self.periods)
+ result.site_group_data = self.site_group_data
+ result.is_reversed = not self.is_reversed
return result
--
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