logo Low Scaling Quantum Chemistry (LSQC) Program

1. Introduction

Low Scaling Quantum Chemistry (LSQC) program is a quantum chemistry package for linear or low scaling electronic structure calculations of large systems, which is developed by the research group of Professor Shuhua Li and Professor Wei Li in Nanjing University. The original version is LSQC-1.0 published on April 20, 2006, and the current version is LSQC-2.4 published on October 1, 2019. Current LSQC program supports two methods developed by Li group. The first one is the generalized energy-based fragmentation (GEBF) method and the other one is the cluster-in-molecule (CIM) local correlation method. Both methods can achieve linear scaling for electronic structure calculations of large systems and have high parallel efficiency.

2. License and Documentation

  • To request a binary copy of LSQC program, please complete the LICENSE FORM, scan and email it to lsqc@nju.edu.cn
  • Download the LSQC Manual (Chinese, English)

3. Modules

(1) Generalized energy-based fragmentation (GEBF) approach

Within the GEBF approach, the total energy of a macromolecule can be directly obtained from the energies of a series of subsystems, which can be obtained from running conventional quantum chemistry calculations. The approach can lead to good results for close-shell systems with localized electrons, such as biomolecules and polymers. For systems with hundreds and even thousands of atoms, the GEBF-X approach allows full quantum mechanical (QM) calculations at the X level to be accessible on ordinary workstations.

The calculations of electrostatically embedded subsystems at various theoretical levels can be done with existing quantum chemistry programs. In this version, only Gaussian program is supported for subsystem calculations.

The single point calculation (SP) at semi-empirical method (AM1, PM3, PM6, etc), HF, DFT and electronic correlation method (MP2, MP3, MP4, CCSD, CCSD(T)) is available in current version. And the geometry optimization (Opt), frequency (Freq), IR intensity, Raman intensity, zero-point energy, enthalpy, Gibbs free energy, dipole moment, static polarizability, hyperpolarizability and NMR are also available in this version.

(2) Cluster-in-molecule (CIM) approach

Within the CIM approach, electronic correlation equations are solved within the representation of occupied and virtual localized molecular orbitals. For a target molecule, the clusters are built from localized molecular orbitals automatically by the program. The approximate correlation energy of the target molecule is obtained from the correlation energy contributions of a series of clusters, which are solved independently. Single point energy at CIM-MP2 and CIM-RI-MP2 levels is available in current version. In addition, conventional MP2 and RI-MP2 calculations for medium-sized systems are also supported.

4. References

All publications resulting from use of this program must cite the following two references.

  • W. Li, C. Chen, D. Zhao, and S. Li, Int. J. Quantum Chem. 115, 641 (2015). DOI: 10.1002/qua.24831.
  • S. Li, W. Li, Y. Jiang, J. Ma, T. Fang, W. Hua, S. Hua, H. Dong, D. Zhao, K. Liao, W. Zou, Z. Ni, Y. Wang, X. Shen and B. Hong, LSQC Program, Version 2.4, Nanjing University, Nanjing, 2019, see http://itcc.nju.edu.cn/lsqc.

Depending on which programs are used, the following references should be cited.

GEBF approach:

All publications calculated with GEBF module should cite the following references:
[1] W. Li, S. Li, and Y. Jiang, J. Phys. Chem. A., 111, 2193 (2007).
[2] W. Hua, T. Fang, W. Li, J.-G. Yu, and S. Li, J. Phys. Chem. A, 112, 10864 (2008).
[3] S. Hua, W. Hua, S. Li, J. Phys. Chem. A, 114, 8126 (2010).
[4] S. Li, W. Li, and J. Ma, Acc. Chem. Res., 47, 2712 (2014).

The license of Gaussian should be available for you and cited if Gaussian program is employed for subsystems calculations. See http://www.gaussian.com/ for more information.

For specific methods, more references should be cited as follows:
(1) two-fragment-centered (frag=twofc):
S. Hua, W. Li, S. Li, ChemPhysChem., 14, 108 (2013).
(2) GEBF-NMR calculation
D. Zhao, R. Song, W. Li, J. Ma, H. Dong, and S. Li, J. Chem. Theory Comput., 13, 5231(2017).

CIM approach:

The following references should be cited if the CIM approach is used:
[1] S. Li, J. Ma, and Y. Jiang, J. Comput. Chem., 23, 237 (2002).
[2] S. Li, J. Shen, W. Li, and Y. Jiang, J. Chem. Phys., 125, 074109 (2006).
[3] W. Li, P. Piecuch, J. R. Gour, and S. Li, J. Chem. Phys., 131, 114109 (2009).
[4] W. Li, P. Piecuch, J. Phys. Chem. A, 114, 8644 (2010).
[5] W. Li, Z. Ni, and S. Li, Mol. Phys., 114, 1447 (2016).
[6] Z. Ni, W. Li, and S. Li, J. Comput. Chem., 40, 1130 (2019).

In the present version, Hartree-Fock calculations are performed by the PySCF package and the electron integrals are used Libcint electron integral library. The reference are:
[1] Q. Sun, T. C. Berkelbach, N. S. Blunt, G. H. Booth, S. Guo, Z. Li, J. Liu, J. McClain, E. R. Sayfutyarova, S. Sharma, S. Wouters, and G. K.-L. Chan, WIREs Comput. Mol. Sci., 8: e1340 (2018).
[2] Q. Sun, J. Comput. Chem., 36, 1664 (2015).