Z2Pack

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52 discussions

Chern number calculation
by Surasree Sadhukhan 02 Apr '21

02 Apr '21

Dear Sir, Are there any extra tags to calculate the Chern number of a system in Z2-pack software? I don't find any tags related to chern number in run.py. Thanks & Regards Surasree Sadhukhan Research Scholar School Of Physical Sciences IIT GOA

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Output for Bi Example
by Johnson, Nathan 02 Feb '21

02 Feb '21

Dear recipient, I have Z2Pack 2.1.1 set up with first principles code as Quantum Espresso version 6.4.1 with interface to Wannier90 3.1.0. I have run calculations for Z2Pack's Bi example and would like to see how our output compares. Calculations have been performed for two Bi systems with pseudopotentials Bi.pbe-dn-kjpaw_psl.1.0.0.UPF<https://www.quantum-espresso.org/upf_files/Bi.pbe-dn-kjpaw_psl.1.0.0.UPF> and Bi.pbe-d-mt.UPF using the provided run.py script. These pseudopotentials were used instead of the supplied pseudopotential as the error, " Error in routine readpp (1): file ../input/Bi_MT_PBE.UPF not readable ", was returned during an attempted SCF run using the pseudopotential. The values used for converge parameters were the same values as those corresponding to converge parameters in the _run.py file located in the 'surface' folder of the Z2Pack 2.1.1 distribution. What ought the output for this example be? I have found a Z2Pack WCC plot corresponding to 'half the kz=0 plane of Bismuth' on page 82 of the Topological Matter School Lectures, however, the surfaces of the example seem to be half the kx=0 and kx=0.5 planes. With the working assumption that the allotrope of Bi corresponding to the Topological Matter School plot is the same allotrope of Bi as that for which the ionic configuration of the example corresponds to, I also performed calculations for both Bi systems using ‘surface=lambda s, t: [t, s / 2, 0]’. I am uncertain, however, that the vertical axis of the WCC plots generated by calculations on this surface would correspond to the x-axis of direct space. I attach the output of aforementioned calculations - please find attached the .win file for both Bi systems and WCC plots. Looking forward to hearing from you, Best wishes, Nathan Johnson, PhD student UK

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Does the Z2pack can run with Quantum Espresso 6.6
by Yubin Fu 15 Dec '20

15 Dec '20

Dear Dr. Gresch, Thank you very much for developing the Z2pack. Recently I am learning to use Z2pack to investigate 1D GNRs. But I have some problems when I start the example of Bismuth by using QE6.6 with Wannier90? on HPC. The error is: AttributeError: 'NoneType' object has no attribute 'find'. I checked it from the Internet, it seems there are many different reasons. I checked the position of 'find'. It is in this part: # Copying the lattice parameters from bi.save/data-file.xml into bi.win cell = ET.parse('scf/bi.save/data-file-schema.xml').find('CELL').find('DIRECT_LATTICE_VECTORS') unit = cell[0].attrib['UNITS'] lattice = '\n '.join([line.text.strip('\n ') for line in cell[1:]]) I checked the data-file.xml and found the 'cell' part but no 'DIRECT_LATTICE_VECTORS' part. So it is because of the absence of 'DIRECT_LATTICE_VECTORS' part that causes the error? Or you have better suggestions. I out the run.py and data-file.xml file in the attachments. It will be great if you can have a check. I also checked the example of the folder in z2pack and found that the Quantum Espresso version is 5.1.1, which is an older version compared with version 6.6. Therefore, the data-file.xml should be the data-file-schema.xml file (I just changed). Also the content of the .xml file in version 5.1.1 is quite different from version 6.6. I cannot find the keyword 'DIRECT_LATTICE_VECTORS' (you can see it in the attachment). Also I'm not sure the following unit and lattice data will be correct. So would you mind to check the run.py file for QE6.6? I found that I cannot do it by myself. Thank you very much in advance. Best regards, Yubin Dr. Yubin Fu Technische Universität Dresden Faculty of Science Department of Chemistry and Food Chemistry Chair of Moleculare Functional Materials Bergstraße 66 New Chemistry Building, Room 253 01069 Dresden Phone: +49 351 463 43259 E-Mail: yubin.fu(a)tu-dresden.de

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Problem to run Z2-pack
by Surasree Sadhukhan 13 Nov '20

13 Nov '20

Dear Sir, I am Surasree Sadhukhan, a research scholar of IIT Goa, India. I am a new user of Z2-pack. But I am getting some errors when I am trying to run run.py. Here I am attaching the screenshot of the errors and run.py. Please let me know how to remove the above errors. looking for your kind reply. <z2pack%40lists.phys.ethz.ch> Thanks & Regards Surasree Sadhukhan Research Scholar School Of Physical Sciences IIT GOA

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question haldane model
by Rafael Gonzalez Hernandez 03 Aug '20

03 Aug '20

Dear z2pack, I used the code to understand the example of Haldane model. However, I changed the bands flag to test it and I found the Chern number for different values of: band=0 chern= doesn't work band=1 chern=-1 band=[0] chern=-1 band=[1] chern=1 band=[0,1] chern=0 Why It is finding found a different between 1(both bands according to manual) and [0,1] bands? Thank you in advance for your help Best regards, -- [image: Resultado de imagen para uninorte logo] Rafael J. González Hernández Profesor Asociado Departamento de Física. Of. 2-45. Bloque L-6. Tel. +57 5 3509509 Ext. 3425 E <http://www.uninorte.edu.co/>mail: rhernandezj(a)uninorte.edu.co -- *Este correo no representa opinión o consentimiento oficial de la Universidad del Norte, por lo que esta no adquiere ninguna responsabilidad por su contenido, salvo en el caso de funcionarios en ejercicio de atribuciones reglamentarias. Puede provenir de una cuenta ofrecida a funcionarios o estudiantes, como parte del ejercicio educativo, evento en el cual tanto el mensaje como sus anexos son estrictamente confidenciales. Ha sido analizado con software antivirus; no obstante, no se garantiza que sea seguro o no contenga errores o virus, por lo que la Universidad del Norte no se hace responsable de su transmisión.*

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Asking help for z2pack
by 毛宁 30 May '20

30 May '20

Dear Sir: Recently, I obtain a strange picture about HWCC and I can't tell about whether it's nontrivial or trivial. For the one hand, white circle clearly show about its trivial topology. For the other hand, Blue circle did go through the white circle for five times and testify its nontrivial topology. Can you give me some advices? PS, the system doesn't have a time reversal symmetry. Have a nice day. Best wished, Ning Mao

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Z2 calculations with first principles code
by raagya＠jncasr.ac.in 20 May '20

20 May '20

Dear Sir, I am a second-year Ph.D. student. I need some help in understanding z2 calculations using first-principles code. How to clearly distinguish strong topological insulator with a weak topological insulator using z2 pack calculations with first principles. What is the difference between the following two cases. What does it signify: 1. Z2 topological invariant at kz = 0: 1 Z2 topological invariant at kz = 0.5: 1 (Both 1) 2. Z2 topological invariant at kz = 0: 0 Z2 topological invariant at kz = 0.5: 1 (Only 1 at one surface) It would be very helpful for my research work if I get some clarity on this. With warm regards, Raagya Arora JNCASR Bangalore, India

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problem about Z2pack
by 黄伟杰 07 Nov '19

07 Nov '19

Dear greschd, I am a greenhand in z2pack. I have read the tutorial and written a program according to PRL 111, 056402 (2013) .However, I don't get the correct answer. I guess some problems in program. The article and program is in appendix. Best wishes Weijie Huang

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problem about Z2pack
by jwh235＠mail.ustc.edu.cn 07 Nov '19

07 Nov '19

1 0

Help regarding chern number calculation
by MS. PRIYANKA SINHA 01 Jun '19

01 Jun '19

Dear Sir, I am a new user of z2 pack and trying to calculate chern number following the journal https://journals.aps.org/prb/pdf/10.1103/PhysRevB.85.115439 . I have defined the Hamiltonian as given in equation 14. I should get non-zero chern number. But instead of that I am getting zero. I am attaching my code below. Kindly help me in this regard. ********************************************************************* #!/usr/bin/env python # -*- coding: utf-8 -*- # # Author: Dominik Gresch <greschd(a)gmx.ch> # Date: 16.08.2016 14:25:39 CEST # File: haldane.py import json import logging import z2pack import numpy as np import matplotlib.pyplot as plt from numpy import linalg as LA logging.getLogger('z2pack').setLevel(logging.WARNING) # defining pauli matrices identity = np.identity(2, dtype=complex) pauli_x = np.array([[0, 1], [1, 0]], dtype=complex) pauli_y = np.array([[0, -1j], [1j, 0]], dtype=complex) pauli_z = np.array([[1, 0], [0, -1]], dtype=complex) Sx= 1./2. * np.array([[0, 1], [1, 0]], dtype=complex) Sy= 1./2. * np.array([[0, -1j], [1j, 0]], dtype=complex) Sz= 1./2. * np.array([[1, 0], [0, -1]], dtype=complex) def Hamilton(k, m, t1, VR): kx, ky,_= k H = (3. *t1 /2. * ( pauli_x * kx + pauli_y * ky)) * identity H += (3. *t1 /2. * (- pauli_x * kx + pauli_y * ky)) * identity H += 3. *VR /2. * ( pauli_x * Sy - pauli_y * Sx) H += 3. *VR /2. * (- pauli_x * Sy - pauli_y * Sx) #H3 = n * 3. *sqrt3 * t2 * pauli_z *Sz H += (m * Sz) * identity #H5 = u * pauli_z * identity return H def get_chern( m, t1, VR, **settings): system = z2pack.hm.System(lambda k: Hamilton(k, m, t1, VR), bands=1) result = z2pack.surface.run(system=system, surface=lambda t1, t2: [t1, t2, 1], **settings) return z2pack.invariant.chern(result) if __name__ == "__main__": # Task a) print(get_chern(0.3, 1., 0.5 )) #print(get_chern(0.5, 1., 1. / 3., -0.5 * np.pi)) #print(Hamilton(0.1, 1, 0.3,0.5)) ******************************************************************** Thanking You, Priyanka Sinha IIT Guwahati Research Scholar

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