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	4028	August 12, 2019
Welcome to the PSI4 Forum!	1	23397	July 16, 2015
Old versions of python	2	2	April 16, 2025
Psi4 "killed" during execution if too many basis/cartesian functions Geometry Optimization	0	4	April 15, 2025
Calculating properties from ESP on an isocontour of electronic density	0	5	April 14, 2025
Software source not found build	2	15	April 11, 2025
CPHF MO gradients from scfgrad/response.cc do not match finite difference values	2	21	April 10, 2025
NMR calculation	0	13	April 8, 2025
C_right_ and C_left_ at jk calculation	3	31	April 4, 2025
FSAPT requires a lot more memory than estimate SAPT	0	35	April 2, 2025
Can a CC Computation Be Restarted?	3	45	March 31, 2025
TDDFT Calculation Crashes	4	49	March 27, 2025
Bug report psio	1	25	March 26, 2025
How Does Psi4 Handle Basis Set Cartesian vs. Spherical GTOs in Quantum Chemistry Calculations	4	59	March 25, 2025
Spin-orbital correction	4	46	March 22, 2025
CCSD calculation with energy('ccsd')	5	50	March 20, 2025
Segmentation fault in fisapt when using DFDirJ+CosX SAPT	0	15	March 19, 2025
Single point job stops over 65 atoms; no error message	1	38	March 13, 2025
DLPNO-CCSD(T) method feature-request	2	97	March 4, 2025
Out of memory using PCM model: Geom. optimization of lithiated ethylene carbonate Geometry Optimization	3	454	March 1, 2025
Def2-universal-jkfit and def2-tzvpp-ri bases? SAPT	0	38	March 1, 2025
Statically-linking Psi4 build	3	52	February 18, 2025
Investigating a chalcogen interaction with i-sapt SAPT	0	36	February 15, 2025
Challenges in Locating the Transition State for Meisenheimer Complex Formation in the SNAr Reaction of 4-Chloropyridine with Azide Anion Geometry Optimization	0	22	February 14, 2025
Error when using psi4/resp: Fatal Error: RHF: RHF reference is only for singlets SAPT	1	39	February 13, 2025
Colab GPU Accelerator Config build	0	37	February 9, 2025
UnboundLocalError for geometry optimization of Li4 with python module psi4 Geometry Optimization	2	31	February 3, 2025
Fractional occupation with PsiAPI	1	23	February 3, 2025
IOH augmented base	2	25	January 27, 2025
One electron Density Matrix diagonals don't sum to 1	9	107	January 22, 2025