The "operation permission" refers to file operation permission in the current folder, it is irrelvant to format of input file. If special reason (e.g. security settings in your operating system, antivirus program...) makes the DISLIN library in Multiwfn unable to normally rewrite or create a file in the current folder, this problem may rise.I strongly suggest you move Multiwfn folder to other partition e.g. D:\ and retry.
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