CI Loop Limit Setting Using Coupled Cluster Energy Gaps
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Solution Overview
Problem
Conventional quantum chemical calculations using the configuration interaction (CI) method face challenges in determining the optimal number of loops, leading to increased execution time and potential inaccuracies due to difficulty in convergence.
Innovation Solution
A method to determine the maximum number of loops for CI calculations based on energy values obtained from coupled cluster methods, specifically CCSD and CCSD(T), adjusting the loop count to optimize execution time and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of loops in CI calculation is increased to improve accuracy, then calculation accuracy is improved, but execution time increases significantly
Solution Approach 1:
The patent performs preliminary coupled cluster calculations (CCSD and CCSD(T)) before the CI calculation to determine an optimal maximum loop count. This preliminary action establishes a data-driven basis for setting the loop limit, avoiding both excessive loops that waste time and insufficient loops that compromise accuracy.
Solution Approach 2:
The patent uses feedback from the coupled cluster calculation results (energy values and loop counts) to dynamically adjust the maximum loop count for the CI calculation. The system feeds back the relationship between loop counts and energy convergence to optimize the CI calculation parameters, creating a closed-loop control system.
2Reliability
If the maximum loop count is set high to ensure convergence, then calculation reliability is improved, but unnecessary processing increases
Solution Approach 1:
The patent changes the parameter (maximum loop count) based on results from coupled cluster calculations. Instead of using a fixed high loop count, the system adjusts this parameter dynamically according to the specific molecular system and convergence behavior observed in preliminary calculations, optimizing both reliability and efficiency.
3Measurement precision
If coupled cluster calculations with different excitation counts are performed to determine optimal loops, then calculation accuracy is improved, but initial processing time increases
Solution Approach 1:
The coupled cluster calculations are performed as preliminary steps to gather necessary data for optimizing the main CI calculation. The time invested in these preliminary calculations is offset by the significant time savings achieved during the main calculation through optimized loop count selection.
Solution Approach 2:
The patent uses relatively inexpensive and computationally efficient coupled cluster methods (CCSD and CCSD(T)) as disposable preliminary calculations to inform the more expensive CI calculation. These preliminary calculations are sacrificed to optimize the overall process, providing necessary information without requiring excessive computational resources.
Data Source
AI summary
A computer-readable recording medium stores therein a number-of-loops adjustment program for causing a computer to execute a process including: determining a maximum number-of-loops when a quantum chemical calculation using a configuration interaction method is executed for a substance under analysis, the maximum number-of-loops being determined based on: a first energy value obtained by the quantum chemical calculation using a first coupled cluster method for the substance under analysis, a second energy value obtained by the quantum chemical calculation using a second coupled cluster method having a different maximum excitation count from the first coupled cluster method for the substance under analysis, and a number-of-loops of the first coupled cluster method when the first energy value is obtained.