Psi4 – Open-Source Quantum Chemistry

Topic	Replies	Views	Activity
Making Topics that Get Answered Most questions that are answered on the Psi4 Forums are answered by a small group of developers and powerusers. Their time and energy is divided between their own research, further Psi development, and helping users. Acc…	2	4180	August 12, 2019
Welcome to the PSI4 Forum!	1	23501	July 16, 2015
Counterpoise correction and projected Hessian	2	54	November 18, 2025
Freezing Cartesian Errors Geometry Optimization	2	28	November 14, 2025
Exporting Natural Orbitals as wfn object to PsiAPI Python interface build	1	32	October 30, 2025
Exporting natural orbitals	0	19	October 27, 2025
Eom-cc2, eom-cc3 for triplet state	0	35	October 23, 2025
Questions on Psi4 performance and scaling on HPC systems build	0	62	September 12, 2025
All vibrational calculation by DFT falied due to UnicodeDecodeError	1	55	August 29, 2025
Error on Windows 10 Installation	0	42	August 22, 2025
Warning message when writing a Molden file + Molden file from MPx calculations	0	24	August 15, 2025
DKH Hamiltonian 4th order SCF convergence issues	0	34	August 3, 2025
Intruder states in FCI	1	55	June 27, 2025
How to obtain atomic charge distribution for a molecule?	1	56	June 27, 2025
Psi4 Conda Environment MPI Init Error	0	37	June 26, 2025
Matmul error when running geometry optimization	2	41	June 25, 2025
IRC optimization fails with "Math Domain Error" Geometry Optimization	3	184	June 18, 2025
NMR calculation	2	98	June 11, 2025
PSI4 Plugin Interface Developer News & Discussion	0	35	June 10, 2025
New to psi4! I can't get psi4 to work with py 3.12 only 3.7	0	62	June 9, 2025
Psi4 1.6 installer is down	0	25	June 9, 2025
PSA: Psi4 Installers Down	1	88	June 9, 2025
SAPT with external point charges SAPT	0	48	June 8, 2025
Slow CBS frequency calculation	0	24	June 6, 2025
Convert Geometry object to Angstrom	2	50	June 6, 2025
No exception thrown at unconverged geometry opt (geomeTRIC) Geometry Optimization	2	36	May 20, 2025
DFT First order hyperpolarizability (beta) feature-request	0	26	May 16, 2025
Failing convergence of Flexible Molecule - Back transformation failed Geometry Optimization	0	69	May 16, 2025
FREEZE_ALL_DIHEDRALS not valid	1	25	May 15, 2025
Extract force constants from python api?	2	61	May 12, 2025

Making Topics that Get Answered

Most questions that are answered on the Psi4 Forums are answered by a small group of developers and powerusers. Their time and energy is divided between their own research, further Psi development, and helping users. Acc…