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Siam Quantum Version 1.2.8 is a major feature enhancement release



What's new.

  • Minimum Energy Crossing Point (MECP). See Tutorial and FAQ


Please cite this work as:
Siam Quantum, Release 1.2.8,
T.Khamla, K.Maneesai, N. Phutaddauwng, N. Sophonrat, A. Kesorn, and T. Chachiyo,
The Department of Physics, Khon Kaen University, 2013.


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Siam Quantum Version 1.2.6 is a major speed enhancement release



What's new.

  • MP2 mode is fast and requires small storage
  • Multipole approximations of the electron integrals
  • Parallel runs for HF, OPT, and MP2 modes


Please cite this work as:
Siam Quantum, Release 1.2.6,
T.Khamla, K.Maneesai, N. Phutaddauwng, N. Sophonrat, A. Kesorn, and T. Chachiyo,
The Department of Physics, Khon Kaen University, 2013.


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Siam Quantum Version 1.2.5 is a major feature enhancement and bug fix release



What's new.

  • Moller-Plesset Perturbation Theory (MP2) Calculations
  • Calculated results can be stored in a checkpoint file
  • Fix bug related to DIIS convergence
  • Compute dipole moment of molecules. See ref. Aniwat Kesorn (2012)


Please cite this work as:
Siam Quantum, Release 1.2.5,
T.Khamla, K.Maneesai, N. Phutaddauwng, N. Sophonrat, A. Kesorn, and T. Chachiyo,
The Department of Physics, Khon Kaen University, 2012.


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Siam Quantum Version 1.2.4 is a minor speed enhancement release



What's new.

  • DIIS method allows faster convergence.
  • Partially store integrals in memory to avoid repetitions (see -MAXMEM option)
  • Better schwarz screening of primitive Gaussian functions to avoid small integrals
  • Yet another recursive relation of Taketa et al. method (1969)
  • Electrostatic properties calculations such as electric potential and field. See ref. Nanta Sophonrat (2011)
  • Add-in contribution: Quantum Molecular Dynamics (src\contrib\qmd). See ref. Chutchawan Jaisuk (2011)


Please cite this work as:
Siam Quantum, Release 1.2.4,
T.Khamla, K.Maneesai, N. Phutaddauwng, N. Sophonrat, and T. Chachiyo,
The Department of Physics, Khon Kaen University, 2011.


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Siam Quantum Version 1.2.3 is a major feature enhancement release



What's new.

  • Geometry optimization is now available. In partial fulfillment of his master degree thesis, Mr. Theerapon Khamla has implemented the calculation of forces acting on nuclei within a molecule which makes it possible to predict the three dimensional structure of the molecule using only a fundamental equation of quantum mechanics: the Schrödinger equation.
  • Mulliken population analysis


Please cite this work as:
Siam Quantum, Release 1.2.3,
T.Khamla, K.Maneesai, N. Phutaddauwng, N. Sophonrat, and T. Chachiyo,
The Department of Physics, Khon Kaen University, 2010.


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Siam Quantum Version 1.2.2 is a major bugfix and performance improvement release



What's new.

  • Export molecular orbitals in Gaussian format using option -GAUSSIAN so that it can be visualized using Gabedit program
  • The Nitrogen molecule problem solved
  • About 4 times faster than the previous version due to i) Better handling of memory usage, ii) Use weighted density matrix coupled with Schwarz pre-screening, iii) compute change of Fock matrix instead of its absolute value, and iv) using identity matrix as an initial guess for density matrix making it converges faster
  • Increase accuracy due to smaller Schwarz cutoff value



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Siam Quantum Version 1.2.1 is a minor bug fix release


What's new.

  • Nanta Sophonrat fix bug regarding electron density calculation during unrestricted hartree-fock post SCF
  • Nanta Sophonrat fix bug regarding cube file format. It is not possible to use GabEdit program to visualize cube file produced by Siam Quantum



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Siam Quantum Version 1.2.0 is a major improvement release



What's new.

  • Unrestricted Hartree-Fock calculation which makes it possible to theoretically study an open-shell system such as triplet oxygen molecule. Use option "-M=INTEGER" to control spin multiplicity of the molecule.
  • A little bit faster than previous version due to re-structuring of inner loop
  • More basis set provided such as STO-3G, and 6-31G*. Although you can always download it from BSE database.



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Siam Quantum Version 1.1.0 is a minor improvement and bug fix release



What's new.

  • Much faster! because the 2-electron integrals have been grouped together into "shells". This should be at least 10 times faster than previous version, and it is now feasible to perform calculation on C60 molecule. (Sadly, Siam Quantum is still 4 times slower than GAMESS.)
  • More control over SCF convergence parameters. You can set -SCFDRAG=0.1 if your molecule is difficult to converge
  • Hopefully, the last bug fix when reading XYZ file format.
  • More efficient code when computing electron density.
  • Load density matrix from previous calculation as initial guess for faster convergence using option -LDMATRIX , -SDMATRIX ,and -FDMATRIX



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Siam Quantum Version 1.0.1 is a minor bug fix regarding reading XYZ file format and adding supports for plotting molecular orbitals in CUBE file format.



Siam Quantum Version 1.0.0 is an initial release. It can solve restricted Hartree-Fock equation for molecular system, and perform simple plotting in 3D.



Related software for visualizations and program developments

  • VMD - Visualization
  • Molden - Build molecules
  • Dev-C++ - C/C++ programmer on Windows XP
  • Xming - Enable X-Windows on Windows XP